Lazarus Pascal Requires Chilkat v11.7.0+

Change the Passwords of an Encrypted PDF

See more PDF Protection Examples

Demonstrates the changePasswords operation, which gives an encrypted PDF new user and owner passwords and keeps its algorithm and permissions. The PDF is loaded with its current passwords, the two properties are then set to the new ones, and Protection reads them at the time of the call. Both passwords are replaced, so set both: a property left empty becomes an empty password. Lazarus Pascal

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Pdf,
  Chilkat.JsonObject;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  pdf: TPdf;
  json: TJsonObject;
  jsonOut: TJsonObject;
  reader: TPdf;
  owner: TPdf;

begin
  success := False;

  //  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 encrypted_user_password.pdf

  pdf := TPdf.Create;

  //  Load with the current passwords.
  pdf.UserPassword := 'secret';
  pdf.OwnerPassword := 'owner-secret';
  success := pdf.LoadFile('qa_data/pdf/encrypted_user_password.pdf');
  if (success = False) then
    begin
      WriteLn(pdf.LastErrorText);
      Exit;
    end;

  //  The new passwords.  Protection reads the properties as they are when it is called.
  pdf.UserPassword := 'new-user-secret';
  pdf.OwnerPassword := 'new-owner-secret';

  json := TJsonObject.Create;
  jsonOut := TJsonObject.Create;
  success := pdf.Protection('changePasswords',json,jsonOut);
  if (success = False) then
    begin
      WriteLn(pdf.LastErrorText);
      Exit;
    end;

  //  The algorithm and the permissions are kept.
  WriteLn('algorithm: ' + jsonOut.StringOf('pending.algorithm'));
  WriteLn('password needed to open: ' + jsonOut.BoolOf('pending.userPasswordRequired'));

  success := pdf.WriteFile('qa_output/minutes_new_passwords.pdf');
  if (success = False) then
    begin
      WriteLn(pdf.LastErrorText);
      Exit;
    end;

  //  The new user password opens the result.
  reader := TPdf.Create;
  reader.UserPassword := 'new-user-secret';
  success := reader.LoadFile('qa_output/minutes_new_passwords.pdf');
  if (success = False) then
    begin
      WriteLn(reader.LastErrorText);
      Exit;
    end;
  success := reader.Protection('getInfo',json,jsonOut);
  if (success = False) then
    begin
      WriteLn(reader.LastErrorText);
      Exit;
    end;
  WriteLn('with the new user password, opened with: ' + jsonOut.StringOf('loaded.openedWith'));

  //  And so does the new owner password.
  owner := TPdf.Create;
  owner.OwnerPassword := 'new-owner-secret';
  success := owner.LoadFile('qa_output/minutes_new_passwords.pdf');
  if (success = False) then
    begin
      WriteLn(owner.LastErrorText);
      Exit;
    end;
  success := owner.Protection('getInfo',json,jsonOut);
  if (success = False) then
    begin
      WriteLn(owner.LastErrorText);
      Exit;
    end;
  WriteLn('with the new owner password, opened with: ' + jsonOut.StringOf('loaded.openedWith'));

  //  Sample output:

  //  algorithm: rc4-128
  //  password needed to open: True
  //  with the new user password, opened with: user
  //  with the new owner password, opened with: owner


  pdf.Free;
  json.Free;
  jsonOut.Free;
  reader.Free;
  owner.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.