// Determine if a file is password protected
function PdfFileIsPasswordProtected(const Filename: string): Boolean;
var
  iev: TImageEnView;
begin
  Result := False;
  try
    iev := TImageEnView.Create(nil);
    try
      iev.PdfViewer.Enabled := True;
      iev.IO.LoadFromFilePDF( Filename, -1, -1, '' );
    finally
      iev.Free;
    end;
  except
    on e: Exception do
      if e.Message = RsPdfErrorPassword then  // Defined in iexPdfiumCore = 'Invalid password'
        Result := True;
  end;
end;