Dart Requires Chilkat v11.7.0+

Password-Protect a PDF with AES-256 Encryption

See more PDF Protection Examples

Demonstrates the simplest way to encrypt a PDF so that it needs a password to open. The passwords come from the UserPassword and OwnerPassword properties, and Protection with the encrypt operation and an empty JSON uses the defaults: AES-256, everything encrypted, every permission granted. Protection only records the security the PDF will be saved with. Nothing is encrypted until WriteFile is called. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  // The PDF used in this example is available at two_page_memo.pdf

  final pdf = CkPdf();
  try {
    pdf.loadFile('qa_data/pdf/two_page_memo.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // The passwords are taken from these two properties at the time Protection is called.
  // The user password opens the PDF.  The owner password opens it too, and is the one needed
  // later to change or remove the protection.
  pdf.userPassword = 'user-secret';
  pdf.ownerPassword = 'owner-secret';

  // An empty JSON asks for the defaults: AES-256, everything encrypted, every permission granted.
  final json = CkJsonObject();
  final jsonOut = CkJsonObject();
  try {
    pdf.protection('encrypt', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Nothing has been encrypted yet.  "pending" describes the security the PDF will be saved with.
  print('algorithm: ${jsonOut.stringOf('pending.algorithm')}');
  print('PDF version: ${jsonOut.stringOf('pending.pdfVersion')}');
  print('password needed to open: ${jsonOut.boolOf('pending.userPasswordRequired')}');

  // Writing the file applies it.
  try {
    pdf.writeFile('qa_output/memo_encrypted.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // PreLoadCheck reports a file's encryption without loading it, and needs no password.
  final checker = CkPdf();
  final info = CkJsonObject();
  try {
    checker.preLoadCheck('qa_output/memo_encrypted.pdf', info);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('encrypted: ${info.boolOf('encrypted')}');
  print('openPasswordRequired: ${info.boolOf('openPasswordRequired')}');

  // With the password, the PDF opens normally.
  final reader = CkPdf();
  reader.userPassword = 'user-secret';
  try {
    reader.loadFile('qa_output/memo_encrypted.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('pages: ${reader.numPages}');

  // Sample output:

  // algorithm: aes-256
  // PDF version: 1.7
  // password needed to open: True
  // encrypted: True
  // openPasswordRequired: True
  // pages: 2
}