PDFBox - Encrypting a PDF Document

In the previous chapter, we have seen how to insert an image in a PDF document. In this chapter, we will discuss how to encrypt a PDF document.

Encrypting a PDF Document

You can encrypt a PDF document using the methods provided by StandardProtectionPolicy and AccessPermission classes.
The AccessPermission class is used to protect the PDF Document by assigning access permissions to it. Using this class, you can restrict users from performing the following operations.

• Print the document
• Modify the content of the document
• Copy or extract content of the document
• Add or modify annotations
• Fill in interactive form fields
• Extract text and graphics for accessibility to visually impaired people
• Assemble the document
• Print in degraded quality

The StandardProtectionPolicy class is used to add a password based protection to a document.
Following are the steps to encrypt an existing PDF document.

Step 1: Loading an Existing PDF Document

Load an existing PDF document using the static method load() of the PDDocument class. This method accepts a file object as a parameter, since this is a static method you can invoke it using class name as shown below.

File file = new File("path of the document") 
PDDocument document = PDDocument.load(file);

Step 2: Creating Access Permission Object

Instantiate the AccessPermission class as shown below.

AccessPermission accessPermission = new AccessPermission();

Step 3: Creating StandardProtectionPolicy Object

Instantiate the StandardProtectionPolicy class by passing the owner password, user password, and the AccessPermission object as shown below.

StandardProtectionPolicy spp = new StandardProtectionPolicy("1234","1234",accessPermission);

Step 4: Setting the Length of the Encryption Key

Set the encryption key length using the setEncryptionKeyLength() method as shown below.

spp.setEncryptionKeyLength(128);

Step 5: Setting the Permissions

Set the permissions using the setPermissions() method of the StandardProtectionPolicy class. This method accepts an AccessPermission object as a parameter.

spp.setPermissions(accessPermission);

Step 6: Protecting the Document

You can protect your document using the protect() method of the PDDocument class as shown below. Pass the StandardProtectionPolicy object as a parameter to this method.

document.protect(spp);

Step 7: Saving the Document

After adding the required content save the PDF document using the save() method of the PDDocument class as shown in the following code block.

document.save("Path");

Step 8: Closing the Document

Finally, close the document using close() method of PDDocument class as shown below.

document.close();

Example

Suppose, we have a PDF document named sample.pdf, in the path C:/PdfBox_Examples/ with empty pages as shown below.
This example demonstrates how to encrypt the above mentioned PDF document. Here, we will load the PDF document named sample.pdf and encrypt it. Save this code in a file with name EncriptingPDF.java.

import java.io.File;
 
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.encryption.AccessPermission;
import org.apache.pdfbox.pdmodel.encryption.StandardProtectionPolicy;
public class EncriptingPDF {
  
   public static void main(String args[]) throws Exception {
      //Loading an existing document
      File file = new File("C:/PdfBox_Examples/sample.pdf");
      PDDocument document = PDDocument.load(file);
   
      //Creating access permission object
      AccessPermission ap = new AccessPermission();         

      //Creating StandardProtectionPolicy object
      StandardProtectionPolicy spp = new StandardProtectionPolicy("1234", "1234", ap);

      //Setting the length of the encryption key
      spp.setEncryptionKeyLength(128);

      //Setting the access permissions
      spp.setPermissions(ap);

      //Protecting the document
      document.protect(spp);

      System.out.println("Document encrypted");

      //Saving the document
      document.save("C:/PdfBox_Examples/sample.pdf");
      //Closing the document
      document.close();

   }
}

Compile and execute the saved Java file from the command prompt using the following commands.

javac EncriptingPDF.java
java EncriptingPDF

Upon execution, the above program encrypts the given PDF document displaying the following message.

Document encrypted

If you try to open the document sample.pdf, you cannot, since it is encrypted. Instead, it prompts to type the password to open the document as shown below.