title: How to add watermark on existing pdf file
body: <p>I am trying to add watermark on pdf file using PdfSharp, I tried from this link </p>
  
  <p><a href="http://www.pdfsharp.net/wiki/Watermark-sample.ashx" rel="nofollow noreferrer">http://www.pdfsharp.net/wiki/Watermark-sample.ashx</a></p>
  
  <p>but am not able to get how to get the existing pdf file page object and how to watermark on that page.</p>
  
  <p>Help?</p>