Itextsharp creates a corrupted pdf after stamping some text
<p>Just stamping some text into a pdf and itextsharp creats a corrupted file. When tried to read the pdf it throws error as follows</p>

<blockquote>
  <p>An exception of type 'iTextSharp.text.exceptions.InvalidPdfException' 
  Additional information: The document has no page root (meaning: it's an invalid PDF).    </p>
</blockquote>

<p>Following code is used to edit the pdf and stamp text content</p>

<pre><code>using (PdfReader pdfReader = new PdfReader(System.IO.File.ReadAllBytes(pdfPath)))
           using (Stream pdfStream = new FileStream(pdfPath, FileMode.Open, FileAccess.ReadWrite))
           {
               PdfReaderContentParser parserReason = new PdfReaderContentParser(pdfReader);
               PdfStamper pdfStamper = new PdfStamper(pdfReader, pdfStream);
               PdfContentByte pdfContentByte = pdfStamper.GetOverContent(pdfReader.NumberOfPages);
               BaseFont baseFont = BaseFont.CreateFont(BaseFont.COURIER_BOLD, BaseFont.CP1250, BaseFont.NOT_EMBEDDED);
               pdfContentByte.SetColorFill(BaseColor.BLACK);
               pdfContentByte.SetFontAndSize(baseFont, 12);
               pdfContentByte.BeginText();
               TextMarginFinder finderReason = parserReason.ProcessContent(pdfReader.NumberOfPages, new iTextSharp.text.pdf.parser.TextMarginFinder());
               pdfContentByte.ShowTextAligned(PdfContentByte.ALIGN_LEFT, "Some text  : " + annotation, finderReason.GetLlx(), finderReason.GetLly() - 20f, 0);
               pdfContentByte.EndText();
               pdfStamper.Close();

           }
</code></pre>

<p>The pdf files are created with apache fop 1.1 and itextsharp is used to edit the file.The issue is not happening with all pdf but only with some files.
 <a href="https://www.dropbox.com/s/ibyoyoeimwt9i4p/Issue%20creating.pdf?dl=0" rel="nofollow">You can find the PDF which creates the issue here</a></p>