PDF password protection

In this tutorial, I am going to show you how to protect a PDF document by passwords so that users that do not have permissions cannot open or modify the content of the PDF document. You can set two passwords to the PDF document,  a user password and an owner password. The user password must be entered before the PDF document can be opened in Adobe Reader or Foxit Reader. The owner password applies restrictions to the PDF document. For example, you can  allow only printing and copying to the PDF document.
By using iText library you can set the passwords to the PDF document by using the setEncryption method of PdfWriter class. The general form of the setEncryption method is shown below:

setEncryption(byte[] userPassword, byte[] ownerPassword, int permissions, int encryptionType)

- userPassword--an array of bytes that is the user password.

- ownerPassword--an array of bytes that is the owner password.

- permissions--permissions or restrictions that will be applied to the PDF document. These permissions can be AllowPrinting, AllowCopy, AllowScreenReaders, AllowFillIn, AllowAssembly, or AllowDegradedPrinting.
- encryptionType--the type of encryption. The encryption type can be one of the following STANDARD_ENCRYPTION_40, STANDARD_ENCRYPTION_128 or ENCRYPTION_AES128.

Example:

import java.awt.Desktop;
import java.io.File;
import java.io.FileOutputStream;
import com.itextpdf.text.Document;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.pdf.PdfWriter;



public class PdfItext {
public static void main(String[] args){
setPasswords();
}

static void setPasswords(){
try{
//create a document object
Document doc = new Document();
//FileOutputStream object to write the pdf file
String path="d:/pdfdocprotected.pdf";
FileOutputStream fos=new FileOutputStream(path);
//get PdfWriter object
PdfWriter writer =PdfWriter.getInstance(doc,fos);
//convert strings of passwords to arrays of bytes
byte[] USER="Hello".getBytes();
byte[] OWNER="world".getBytes();
//spcify encryption of the document
writer.setEncryption(USER, OWNER, PdfWriter.ALLOW_PRINTING,

PdfWriter.ENCRYPTION_AES_256);          
      writer.createXmpMetadata();
//open the document for writing
doc.open();
//write a paragraph to the document
doc.add(new Paragraph("This PDF document is protected."));
//close the document
doc.close();
//view the result pdf file
Desktop dt=Desktop.getDesktop();
if(Desktop.isDesktopSupported()){
dt.open(new File(path));
}
}catch(Exception e){e.printStackTrace();}
}
}

When you run the example code above, you might get the dependency error as shown below. To fix the error, you will download the extra jar files from http://sourceforge.net/projects/itext/files/extrajars/. Then extract the zip file and add the bcprov-jdk15on-1.48.jar file to the project. After that, run the program again.