PDFExplorer Class

Properties   Methods   Events   Config Settings   Errors  

The PDFExplorer class provides access to the low-level PDF document structure.

Syntax

securepdf.PDFExplorer

Remarks

The PDFExplorer class can be used to inspect the internals of a PDF document and make changes to the low-level document structure.

Object Types and Document Structure

The PDF specification defines eight object types:

• Name
• String
• Real
• Integer
• Boolean
• Array
• Dictionary
• Stream

Before accessing individual objects with the class, it is important to understand how they are structured in the document. PDFExplorer aims to distinguish between the logical and physical representations of objects.

The logical representation is that a PDF document is a tree of objects that can be traversed to extract data. For example, every document contains a document catalog that references a next-level object /Pages, which in turn references individual pages via a /Kids array. So to get a page, you would first look for the /Root object in the document trailer, then proceed to its /Pages element, and then work with the /Kids array.

Then, there is the physical structure that consists of all the objects that constitute the document. Every object is recorded as either:

• A direct (in-place) object (e.g., /Numbers [1 2 3 888]),
• An indirect (numbered) object, or
• A reference to an indirect object (e.g., /Numbers 8 0 R).

Note that most heavy objects (such as streams and dictionaries) are recorded in PDF files as indirect objects, with other objects referencing them. An indirect object is a global object that is uniquely identified by its object number followed by its generation number (e.g., 1 0 obj).

Navigating the Document

These objects can then be used as a starting point for the document tree navigation, which is done using the Select method. This method and others operate the following syntax for specifying objects in the document:

• Slashes separate levels of hierarchy, like in file paths.
• The "root" slash (/) points to the document trailer dictionary.
• A path that does not start with a slash specifies an indirect object in the list of global numbered objects.
• The asterisk character (*) specifies all objects at the provided path.

Consider the following PDF document:

%PDF-1.4
%cmmt
1 0 obj
<< /Type /Catalog
/Pages 2 0 R
>>
endobj

2 0 obj
<< /Type /Pages
/Kids [ 3 0 R ]
/Count 1
>>
endobj

3 0 obj
<< /Type /Page
/Parent 2 0 R
/MediaBox [ 0  0  612  792 ]
/Resources << /ProcSet 4 0 R >>
>>
endobj

4 0 obj
[ /PDF ]
endobj

xref
0 5
0000000000 65535 f
0000000015 00000 n
0000000065 00000 n
0000000125 00000 n
0000000234 00000 n
trailer
<< /Size 5
/Root 1 0 R
>>
startxref
259
%%EOF

Select would return the following results for the respective paths:

• / - a dictionary object that corresponds to the trailer dictionary.
• /Root - a dictionary object that corresponds to the dictionary at 1 0 obj, with its Disposition field set to Reference (as this is a reference to an indirect object).
• /Size - an integer object whose Value is 5 and Disposition is Direct (as this is a direct, in-place object).
• /Root/Type - a name object whose Value is Catalog (Disposition = Direct).
• /Root/Pages - a dictionary object that corresponds to the dictionary at 2 0 obj (Disposition = Reference).
• /Root/Pages/Kids - an array object (Disposition = Direct).
• /Root/Pages/Kids[0] - a dictionary object that corresponds to the dictionary at 3 0 obj (Disposition = Reference).
• /Root/Pages/Kids[0]/MediaBox - an array object with four integer elements (Disposition = Direct).
• /Root/Pages/Kids[0]/MediaBox[2] - an integer object whose Value is 612 (Disposition = Direct).
• 3 0 obj - a dictionary object that corresponds to the dictionary at 3 0 obj (Disposition = Indirect).
• 3 0 obj/Type - a name object whose Value is Page (Disposition = Direct).
• 3 0 obj/Parent - a dictionary object that corresponds to the dictionary at 2 0 obj (Disposition = Reference).

Adding and Modifying Objects

Primitive Objects

A primitive object is a non-container object that represents a name, string, real (double), integer, or boolean value. Primitive objects are typically stored in-place and referenced directly. Use the AddPrimitive method to add a direct primitive object and the AddObject method (with the Indirect parameter set to true) to add an indirect primitive object: // Adding a direct string object to the /Info dictionary string stringPath = pdfexplorer.AddPrimitive("/Info", "Creator", "Microsoft Word"); // Adding an indirect boolean object to the root string booleanPath = pdfexplorer.AddObject("", 5, "", "true", true);

5 0 obj
<<
...
/Creator (Microsoft Word)
>>
endobj

...

6 0 obj
true
endobj

The value of a primitive object can then be modified if desired: pdfexplorer.Select(stringPath, true); pdfexplorer.SelectedObjects[0].Value = "nsoftware.SecurePDF"; pdfexplorer.Select(booleanPath, true); pdfexplorer.SelectedObjects[0].Value = "false";

5 0 obj
<<
...
/Creator (nsoftware.SecurePDF)
>>
endobj

...

6 0 obj
false
endobj

Array and Dictionary Objects

Unlike primitives, arrays and dictionaries are objects that contain other objects. Elements within array objects are arranged sequentially and have implicit zero-based indices, whereas dictionary objects contain named key-value pairs that are unordered. Use the AddContainer method to add a direct or indirect array or dictionary object: // Adding a direct array object to the first page's /Page dictionary string arrayPath = pdfexplorer.AddContainer("/Root/Pages/Kids[0]", "CropBox", false, false); // Adding an indirect dictionary object to the root string dictPath = pdfexplorer.AddContainer("", "", true, true);

3 0 obj
<< /Type /Page
...
/CropBox [
]>>
endobj

...

7 0 obj
<<
>>
endobj

An array or dictionary object can then be modified by adding elements to it. The example below populates the /CropBox array with four integer objects and adds a /Type key to the newly created dictionary. string cropBox0Path = pdfexplorer.AddPrimitive(arrayPath, "", "0"); string cropBox1Path = pdfexplorer.AddPrimitive(arrayPath, "", "0"); string cropBox2Path = pdfexplorer.AddPrimitive(arrayPath, "", "612"); string cropBox3Path = pdfexplorer.AddPrimitive(arrayPath, "", "792"); string typePath = pdfexplorer.AddPrimitive(dictPath, "Type", "/SampleType");

3 0 obj
<< /Type /Page
...
/CropBox [
0
0
612
792
]>>
endobj

...

7 0 obj
<<
/Type /SampleType
>>
endobj

Stream Objects

A stream object is a compound object consisting of a dictionary and a sequence of bytes. Stream objects are always indirect and are used to store data such as images, fonts, and other resources. Use the AddStream method to add a stream object: // Adding a stream object to the root byte[] image1Data = File.ReadAllBytes("image1.png"); string streamPath = pdfexplorer.AddStream("", "", image1Data);

8 0 obj
<<
/Length 6317
>>stream
... % binary data for image1.png
endstream
endobj

To modify a stream object, use the SetObjectData or SetObjectStream method: byte[] image2Data = File.ReadAllBytes("image2.png"); pdfexplorer.SetObjectData(streamPath, image2Data); // or pdfexplorer.SetObjectStream(streamPath, new MemoryStream(image2Data));

8 0 obj
<<
/Length 197
>>stream
... % binary data for image2.png
endstream
endobj

Object References

An (indirect) object reference is a reference to an indirect object from another object. Its syntax consists of the destination object's object number, its generation number, and R (e.g., 1 0 R). Use the AddReference method to add a reference to an existing object: // Creating a reference to the stream at 8 0 obj and adding it to the dictionary at 7 0 obj string path = pdfexplorer.AddReference("7 0 obj", "Image", "8 0 obj");

7 0 obj
<<
/Image 8 0 R
/Type /SampleType
>>
endobj

The contents of the destination object can be modified using the path returned by AddReference in the same way as any other indirect object - the reference will remain intact because the object and generation numbers of the destination object will not be affected.

Removing Objects

7 0 obj
<<
/Type /SampleType
>>
endobj

When finished adding, modifying, or removing objects, call the Close method to close the document and save the changes to either OutputFile, OutputData, or the stream set in SetOutputStream.

Property List

The following is the full list of the properties of the class with short descriptions. Click on the links for further details.

Method List

The following is the full list of the methods of the class with short descriptions. Click on the links for further details.

Event List

The following is the full list of the events fired by the class with short descriptions. Click on the links for further details.

Config Settings

The following is a list of config settings for the class with short descriptions. Click on the links for further details.

InputData Property (PDFExplorer Class)

A byte array containing the PDF document to process.

Syntax

public byte[] getInputData();
public void setInputData(byte[] inputData);

Remarks

This property is used to assign a byte array containing the PDF document to be processed.

This property is not available at design time.

InputFile Property (PDFExplorer Class)

The PDF file to process.

Syntax

public String getInputFile();
public void setInputFile(String inputFile);

Default Value

""

Remarks

This property is used to provide a path to the PDF document to be processed.

OutputData Property (PDFExplorer Class)

A byte array containing the PDF document after processing.

Syntax

public byte[] getOutputData();

Remarks

This property is used to read the byte array containing the produced output after the operation has completed. It will only be set if an output file and output stream have not been assigned via OutputFile and SetOutputStream respectively.

This property is read-only and not available at design time.

OutputFile Property (PDFExplorer Class)

The path to a local file where the output will be written.

Syntax

public String getOutputFile();
public void setOutputFile(String outputFile);

Default Value

""

Remarks

This property is used to provide a path where the resulting PDF document will be saved after the operation has completed.

Overwrite Property (PDFExplorer Class)

Whether or not the class should overwrite files.

Syntax

public boolean isOverwrite();
public void setOverwrite(boolean overwrite);

Default Value

False

Remarks

This property indicates whether or not the class will overwrite OutputFile, OutputData, or the stream set in SetOutputStream. If set to false, an error will be thrown whenever OutputFile, OutputData, or the stream set in SetOutputStream exists before an operation.

RootObjects Property (PDFExplorer Class)

A collection of all the root objects contained in the document.

Syntax

public PDFObjectList getRootObjects();

Remarks

This property is used to access the list of root objects of the document object tree.

The logical structure of the document (the "root") starts at the document trailer. The trailer contains such entries as /Info and /Root, which provide a pathway for accessing deeper objects such as pages, forms, and signatures.

This property is read-only and not available at design time.

SelectedObjects Property (PDFExplorer Class)

A collection of objects that match the current selection.

Syntax

public PDFObjectList getSelectedObjects();

Remarks

This property is used to access the list of objects that match the selection criteria specified in the Select method.

This property is read-only and not available at design time.

AddContainer Method (PDFExplorer Class)

Adds a dictionary or array object to the document.

Syntax

public String addContainer(String basePath, String objectName, boolean dictionary, boolean indirect);

Remarks

This method is used to add a new dictionary or array object to the document at BasePath. If adding to an existing dictionary, set ObjectName to the key that the new object will be added or referenced under.

The Dictionary parameter specifies whether to create a dictionary object.

The Indirect parameter specifies whether to add the dictionary or array to the indirect (numbered) object list and reference it from BasePath instead of creating an in-place object.

This method returns the path of the new object in the document.

Please see Navigating the Document for more details about object paths.

AddObject Method (PDFExplorer Class)

Inserts an object into the document.

Syntax

public String addObject(String basePath, int objectType, String objectName, String value, boolean indirect);

Remarks

This method is used to add a new object with value Value to the document at BasePath. If adding to an existing dictionary, set ObjectName to the key that the new object will be added or referenced under.

The ObjectType parameter specifies the type of the object and can be one of the following values:

• 1 (Name)
• 2 (String)
• 3 (Real)
• 4 (Integer)
• 5 (Boolean)
• 6 (Array)
• 7 (Dictionary)
• 8 (Stream)

NOTE: This method can be particularly useful to add a primitive object (name, string, real, integer, or boolean) to the list of indirect (numbered) objects.

This method returns the path of the new object in the document.

Please see Navigating the Document for more details about object paths.

AddOpaque Method (PDFExplorer Class)

Adds an opaque piece of PDF to the document.

Syntax

public String addOpaque(String basePath, String objectName, String value);

Remarks

This method is used to add an uninterpreted string of PDF objects with value Value to the document at BasePath. If adding to an existing dictionary, set ObjectName to the key that the new object will be added under.

Example: pdfexplorer.InputFile = "input.pdf"; pdfexplorer.OutputFile = "modified.pdf"; pdfexplorer.Open(); string value = "<< /Producer (Secure PDF)\r\n" + "/CreationDate (D:20250725102001Z00'00')\r\n" + "/ModDate (D:20250725102001Z00'00')\r\n" + "/Author (Edvard Grieg)\r\n" + "/Title (In the Hall of the Mountain King)\r\n" + ">>"; string path = pdfexplorer.AddOpaque("/", "Info", value); pdfexplorer.Close(); This method returns the path of the new object in the document.

Please see Navigating the Document for more details about object paths.

AddPrimitive Method (PDFExplorer Class)

Adds a primitive object to the document.

Syntax

public String addPrimitive(String basePath, String objectName, String value);

Remarks

This method is used to add a new name, string, real (double), integer, or boolean object with value Value to the document at BasePath. If adding to an existing dictionary, set ObjectName to the key that the new object will be added under.

The class will automatically determine the type of the object based on the Value parameter.

Examples: pdfexplorer.InputFile = "input.pdf"; pdfexplorer.OutputFile = "modified.pdf"; pdfexplorer.Open(); // Adding a name object to the dictionary at 3 0 obj string namePath = pdfexplorer.AddPrimitive("3 0 obj", "Type", "/Font"); // Adding a string object to the dictionary at 1 0 obj string stringPath = pdfexplorer.AddPrimitive("1 0 obj", "Name", "John Doe"); // Adding a real object to an array string realPath = pdfexplorer.AddPrimitive("5 0 obj/Rect", "", "100.5"); // Adding an integer object to an array string integerPath = pdfexplorer.AddPrimitive("/Root/Pages/Kids[0]/MediaBox", "", "792"); // Adding a boolean object to a dictionary string booleanPath = pdfexplorer.AddPrimitive("/Root/AcroForm", "NeedAppearances", "true"); pdfexplorer.Close(); This method returns the path of the new object in the document.

Please see Navigating the Document for more details about object paths.

AddReference Method (PDFExplorer Class)

Adds an object reference to the document.

Syntax

public String addReference(String basePath, String objectName, String refPath);

Remarks

This method is used to create a new reference to an existing object, such as a page dictionary, at BasePath. If adding to an existing dictionary, set ObjectName to the key that the new reference will be added under.

The RefPath parameter specifies the destination object and must point to one of the indirect (numbered) objects.

This method returns the path of the new object in the document.

Please see Navigating the Document for more details about object paths.

AddStream Method (PDFExplorer Class)

Adds a stream object to the document.

Syntax

public String addStream(String basePath, String objectName, byte[] value);

Remarks

This method is used to create a new stream object with value Value at BasePath. If adding to an existing dictionary, set ObjectName to the key that the new stream will be referenced under.

NOTE: Stream objects are always indirect (i.e., part of the numbered object list).

This method returns the path of the new object in the document.

Please see Navigating the Document for more details about object paths.

Close Method (PDFExplorer Class)

Closes the opened document.

Syntax

public void close();

Remarks

This method is used to close the previously opened document. It should always be preceded by a call to the Open method.

Example: component.InputFile = "input.pdf"; component.Open(); // Some operation component.Close(); If any changes are made to the document, they will be saved automatically to OutputFile, OutputData, or the stream set in SetOutputStream when this method is called. To configure this saving behavior, set the SaveChanges configuration setting.

Config Method (PDFExplorer Class)

Sets or retrieves a configuration setting.

Syntax

public String config(String configurationString);

Remarks

Config is a generic method available in every class. It is used to set and retrieve configuration settings for the class.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

CreateNew Method (PDFExplorer Class)

Creates a new PDF document.

Syntax

public void createNew();

Remarks

This method is used to create a blank PDF document with one empty page. Having created the baseline document, use the class's methods (such as AddStream) to add objects to it.

GetObjectData Method (PDFExplorer Class)

Returns the content of a stream object.

Syntax

public byte[] getObjectData(String path);

Remarks

This method is used to retrieve the content of the PDF stream object at Path.

Please see Navigating the Document for more details about object paths.

GetObjectStream Method (PDFExplorer Class)

Writes the unparsed and uninterpreted content of a stream object to a stream.

Syntax

public void getObjectStream(String path, java.io.OutputStream outputStream);

Remarks

This method is used to extract the content of the PDF stream object at Path to a stream.

Please see Navigating the Document for more details about object paths.

Open Method (PDFExplorer Class)

Opens the document for processing.

Syntax

public void open();

Remarks

This method is used to open the document specified in InputFile, InputData, or SetInputStream before performing some operation on it, such as accessing or modifying individual PDF objects. When finished, call Close to complete or discard the operation.

It is recommended to use this method (alongside Close) when performing multiple operations on the document at once.

NOTE: This method will populate the RootObjects collection with the keys found in the document trailer dictionary.

RemoveObject Method (PDFExplorer Class)

Removes an object from the document.

Syntax

public void removeObject(String path);

Remarks

This method is used to remove the object at Path from the document.

Note the following peculiarities of the PDF format:

• Certain objects ("indirect objects") are global, numbered objects that can be referenced from other objects in the document. To remove an indirect object, all the references to it must be removed first, followed by the object itself.
• Indirect objects may have more than one reference. Removing such an object may inadvertently invalidate other references in the document.

Reset Method (PDFExplorer Class)

Resets the class.

Syntax

public void reset();

Remarks

This method is used to reset the class's properties and configuration settings to their default values.

Select Method (PDFExplorer Class)

Selects an object or multiple objects from the document.

Syntax

public void select(String filter, boolean clearExistingSelection);

Remarks

This method is used to select objects from the document using an XPath-like language. Upon completion of this method, objects with paths matching the Filter parameter will be populated in the SelectedObjects collection.

The ClearExistingSelection parameter specifies whether SelectedObjects will be cleared before performing the select operation.

NOTE: Since streams are compound objects consisting of a dictionary and data, when selecting a stream object this method will select its dictionary. Use the GetObjectData or GetObjectStream methods to extract the content of stream objects.

Please see Navigating the Document for more details about object paths.

SetInputStream Method (PDFExplorer Class)

Sets the stream containing the PDF document to process.

Syntax

public void setInputStream(java.io.InputStream inputStream);

Remarks

This method is used to set the stream from which the class will read the PDF document to be processed. If an input stream is set before the class attempts to perform operations on the document, the class will read the data from the input stream instead of from the InputFile or InputData properties.

NOTE: It may be useful to additionally set the CloseInputStreamAfterProcessing configuration setting to true when using input streams.

SetObjectData Method (PDFExplorer Class)

Sets the content of a stream object.

Syntax

public void setObjectData(String path, byte[] value);

Remarks

This method is used to set the content of the PDF stream object at Path. The Value parameter specifies the data of the stream.

Please see Navigating the Document for more details about object paths.

SetObjectStream Method (PDFExplorer Class)

Sets the content of a stream object from a stream.

Syntax

public void setObjectStream(String path, java.io.InputStream inputStream);

Remarks

This method is used to set the content of the PDF stream object at Path, providing the data in a stream.

Please see Navigating the Document for more details about object paths.

SetOutputStream Method (PDFExplorer Class)

Sets the stream to write the processed document to.

Syntax

public void setOutputStream(java.io.OutputStream outputStream);

Remarks

This method is used to set the stream to which the class will write the resulting PDF document. If an output stream is set before the class attempts to perform operations on the document, the class will write the data to the output stream instead of writing to OutputFile or populating OutputData.

NOTE: It may be useful to additionally set the CloseOutputStreamAfterProcessing configuration setting to true when using output streams.

Error Event (PDFExplorer Class)

Fired when information is available about errors during data delivery.

Syntax

public class DefaultPDFExplorerEventListener implements PDFExplorerEventListener {
  ...
  public void error(PDFExplorerErrorEvent e) {}
  ...
}

public class PDFExplorerErrorEvent {
  public int errorCode;
  public String description;
}

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the class throws an exception.

The ErrorCode parameter contains an error code, and the Description parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

Log Event (PDFExplorer Class)

Fired once for each log message.

Syntax

public class DefaultPDFExplorerEventListener implements PDFExplorerEventListener {
  ...
  public void log(PDFExplorerLogEvent e) {}
  ...
}

public class PDFExplorerLogEvent {
  public int logLevel;
  public String message;
  public String logType;
}

Remarks

This event is fired once for each log message generated by the class. The verbosity is controlled by the LogLevel configuration setting.

The LogLevel parameter indicates the detail level of the message. Possible values are:

The Message parameter is the log message.

The LogType parameter identifies the type of log entry. Possible values are:

• CertValidator
• Font
• HTTP
• PDFInvalidSignature
• PDFRevocationInfo
• Timestamp
• TSL

PDFObject Type

A single PDF object.

Remarks

This type provides access to the properties of an individual document object.

• Container
• Disposition
• ElementCount
• GenNumber
• Keys
• ObjectNumber
• ObjectType
• Offset
• Path
• Size
• Value

Fields

5 0 obj
<<
  /KeyM (Electricity)
>>

...

<<
  /KeyA (Some Value)
  /KeyB << /X /Y >>
  /KeyC 5 0 R
>>

Constructors

public PDFObject();

public PDFObject( objectType,  path);

Config Settings (PDFExplorer Class)

PDFExplorer Config Settings

Base Config Settings

Trappable Errors (PDFExplorer Class)

PDFExplorer Errors

PDF Errors

Parsing Errors