title: iText or iTextSharp： when i use the ‘PdfStamper’ , target file use adobe.reader Verify signature failure
body: <p>i want remove the last signature and other signature also can use adobe.reader verify_sign success.</p>
  
  <p>the original file is signed and use adobe.reader verify signature success，but when i do this code(i not remove the signature)， the target file use adobe.reader verify signature failed. but when i use adobe.reader open them, their content show ok. </p>
  
  <p>i doubt the function ·PdfStamper· destroyed the signature data. How should i avoid this problem ？</p>
  
  <p>i use itext and itextsharp (Java and C# ) , They are all this problem. itex and itextsharp version is 5.5.10</p>
  
  <p>i find the url  <a href="https://stackoverflow.com/questions/39919205/at-least-one-signature-is-invalid-error-message-after-removing-signature-from?answertab=active#tab-top">&quot;AT least one signature is invalid&quot; error message after removing signature from pdf using itext</a>        it has removed the signature show falied, but i not remove signature, only 'new PdfStamper' ,the target file use adobe.reader verify signature faild.</p>
  
  <p>thanks~</p>
  
  <pre><code>PdfReader re = new PdfReader(filePath);
  PdfStamper pdfStamper = new PdfStamper(re, new FileStream(temfilePath, FileMode.Create));
  //TODO temfilePath verify signature failed.        
  /*
   *    // not do this code
   *     //just remove the last signature.
   *     AcroFields acro = re.AcroFields;
   *     List&lt;string&gt; list = acro.GetSignatureNames();
   *     int i = 0;
   *     foreach (string s in list)
   *       {
   *           if (list.Count == i)
   *           {
   *               acro.ClearSignatureField(s); acro.RemoveField(s);
   *           }
   *           i++;
   *
   *       }
   */     
   pdfStamper.Close();
   re.Close();
  </code></pre>