Java encryption and decryption PDF

This article will show you how to set protection for PDF documents in your Java program. We can display the password to view the document. That is, you can set a password for editing a document that cannot be edited by simply reading the document through this password.

Tools used: Free Spire.PDF for Java V2.0.0

[Example 1] Encrypt a PDF document

import java.util.EnumSet;
import com.spire.pdf.PdfDocument;
import com.spire.pdf.security.PdfEncryptionKeySize;
import com.spire.pdf.security.PdfPermissionsFlags;

public class EncryptPDF {
    public static void main(String[] args) {
        //PdfDocument example to create
        PdfDocument doc = new PdfDocument();
        //Load the PDF file
        doc.loadFromFile("sample.pdf");

        //Encrypt PDF files
        PdfEncryptionKeySize keySize = PdfEncryptionKeySize.Key_128_Bit;
        
        //When you open a document, you just look at it.
        String openPassword = "123456";

        //If you open the document, you can edit it.
        String permissionPassword = "test"; 
        EnumSet flags = EnumSet.of(PdfPermissionsFlags.Print, PdfPermissionsFlags.Fill_Fields);
        doc.getSecurity().encrypt(openPassword, permissionPassword, flags, keySize);

        //Save the file
        doc.saveToFile("Encrypt.pdf");
        doc.close();             
    }
}

After completing the code, run the program and generate the documentation. When you open a document, you can enter the password to find out the specific status of the document's encryption. As below:

[Example 2] Unprotect PDF password

import com.spire.pdf.PdfDocument;
import com.spire.pdf.security.PdfEncryptionKeySize;
import com.spire.pdf.security.PdfPermissionsFlags;

public class DecryptPDF {

    public static void main(String[] args) throws Exception {
        
        //PdfDocument example to create
        PdfDocument doc = new PdfDocument();
        //Load password protected PDF file
        doc.loadFromFile("Encrypt.pdf", "123456");

        //Unprotect passwords in documents
        doc.getSecurity().encrypt("", "", PdfPermissionsFlags.getDefaultPermissions(), PdfEncryptionKeySize.Key_256_Bit, "test");
        
        //Save the file
        doc.saveToFile("Decrypt.pdf");
        doc.close();
    }
}

After running the program, the generated document is no longer password protected.