ItextSharp PDF没有标题

Question

我已经创建了一个控制台应用程序，该应用程序使用内存流来创建pdf文件，对其进行加密并将其添加为附件。

using (Stream output = new MemoryStream())
{
  Document document = new Document();
  using (var stream = new MemoryStream())
  {
    PdfWriter.GetInstance(document, stream);
    document.Open();
    var image = Image.GetInstance(renderedPayslip);
    image.ScaleToFit(600, 820);
    image.SetAbsolutePosition(2, 10);
    document.Add(image);

    using (var newTestStream = new MemoryStream())
    {
      stream.CopyTo(newTestStream);
      newTestStream.Position = 0;

      document.Close();                               

      PdfReader reader = new PdfReader(stream.ToArray());
      PdfStamper stamper = new PdfStamper(reader, newTestStream);     
      PdfEncryptor.Encrypt(reader, newTestStream, true, "secret", "secret", PdfWriter.ALLOW_PRINTING);

      reader.Close();
    }
//return sm.ToArray();
}

问题在于它不断发出消息PDF Header not found。

请帮忙吗？