public function testEscapeString()
 {
     $enc = new \Com\Tecnick\Pdf\Encrypt\Encrypt();
     $result = $enc->escapeString('');
     $this->assertEquals('', $result);
     $result = $enc->escapeString('hello world');
     $this->assertEquals('hello world', $result);
     $result = $enc->escapeString('(hello world) slash \\' . chr(13));
     $this->assertEquals('\\(hello world\\) slash \\\\\\r', $result);
 }