Dart Requires Chilkat v11.7.0+

Find Out Whether a PDF Needs a Password Before Loading It

See more PDF Protection Examples

Demonstrates PreLoadCheck, which examines a PDF file without loading it and without any password. It reports whether the file is encrypted, by which method and algorithm, whether a password is needed to open it, and what its permissions are. An application uses it to decide whether to ask for a password, or which certificate it needs, before calling LoadFile. PreLoadCheckBd does the same for a PDF held in memory. 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

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

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

  final pdf = CkPdf();
  final info = CkJsonObject();

  // A PDF that is not encrypted.  Nothing but "encrypted" is reported for it.
  try {
    pdf.preLoadCheck('qa_data/pdf/two_page_memo.pdf', info);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

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

  // A PDF that needs a password to open.
  try {
    pdf.preLoadCheck('qa_data/pdf/encrypted_user_password.pdf', info);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('encrypted_user_password.pdf');
  print('  encrypted: ${info.boolOf('encrypted')}');
  print('  method: ${info.stringOf('method')}');
  print('  algorithm: ${info.stringOf('algorithm')}');
  print('  openPasswordRequired: ${info.boolOf('openPasswordRequired')}');

  // A PDF that opens without a password but is restricted.  The permissions are readable without
  // any password.
  try {
    pdf.preLoadCheck('qa_data/pdf/no_copy_permission.pdf', info);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('no_copy_permission.pdf');
  print('  encrypted: ${info.boolOf('encrypted')}');
  print('  openPasswordRequired: ${info.boolOf('openPasswordRequired')}');
  print('  may copy: ${info.boolOf('permissions.copy')}');

  // The typical use: ask for a password only when one is needed, then load.
  try {
    pdf.preLoadCheck('qa_data/pdf/encrypted_user_password.pdf', info);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  if (info.boolOf('openPasswordRequired')) {
    // An application would prompt for the password here.
    pdf.userPassword = 'secret';
  }

  try {
    pdf.loadFile('qa_data/pdf/encrypted_user_password.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('loaded, pages: ${pdf.numPages}');

  // Sample output:

  // two_page_memo.pdf
  //   encrypted: False
  // encrypted_user_password.pdf
  //   encrypted: True
  //   method: password
  //   algorithm: rc4-128
  //   openPasswordRequired: True
  // no_copy_permission.pdf
  //   encrypted: True
  //   openPasswordRequired: False
  //   may copy: False
  // loaded, pages: 1
}