java - How to make pdf file password protected?

Question

I want to make pdf file password protected. I just goolge it for the same and find a good solution given below. It's working fine But it wipe out all the data which is already there in my pdf after i secure pdf using below given code.

Used jar files for this code are:

itextpdf-5.2.1.jar

bcmail-jdk16-1.46.jar

bcprov-jdk16-1.46.jar

bctsp-jdk16-1.46.jar

Code to secure PDF :

import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.pdf.PdfWriter;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class Secure_file {
    private static String USER_PASSWORD = "password";
    private static String OWNER_PASSWORD = "secured";
    public static void main(String[] args) throws IOException {
        Document document = new Document();
        try {
            PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream("E:\sample.pdf"));
            writer.setEncryption(USER_PASSWORD.getBytes(),OWNER_PASSWORD.getBytes(), PdfWriter.ALLOW_PRINTING,PdfWriter.ENCRYPTION_AES_128);
            document.open();
            document.add(new Paragraph("This is Password Protected PDF document."));
            document.close();
            writer.close();
        } catch (DocumentException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}

what changes i need to made in this program ?

Answer 1

If you look up the iText in Action keywords you'll find encryption pointing to the sample part3.chapter12.EncryptionPdf. That sample's method createPdf essentially is equivalent to your code but the method encryptPdf is what you want:

/** User password. */
public static byte[] USER = "Hello".getBytes();
/** Owner password. */
public static byte[] OWNER = "World".getBytes();

...

public void encryptPdf(String src, String dest) throws IOException, DocumentException {
    PdfReader reader = new PdfReader(src);
    PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
    stamper.setEncryption(USER, OWNER,
        PdfWriter.ALLOW_PRINTING, PdfWriter.ENCRYPTION_AES_128 | PdfWriter.DO_NOT_ENCRYPT_METADATA);
    stamper.close();
    reader.close();
}