title: PDFBox 2.x detect document changed after signing
body: <p>I'm trying to figure out how to detect if a document has been changed after it has been signed. I can't seem to find a good solution of this.</p>
  
  <p>Anyone know about this?</p>
  
  <p>EDIT<br>
  Did some additional testing using only the "<em>ShowSignature.java</em>". Here is what I found so far. If I change the document through PDFBox, both Adobe Reader &amp; PDFBox will detect the broken signature. If I change the document with an Adobe product (Adobe Illustrator in this case) Adobe will report signature as broken, "<em>ShowSignature.java</em>" will not. 
  Subfilter is <em>ETSI.CAdES.detached</em><br>
  Links to both working and broken:</p>
  
  <ul>
  <li><a href="https://www.dropbox.com/s/j2du1s7rfwx8vge/tampered.pdf?dl=0" rel="nofollow noreferrer">Broken signature</a></li>
  <li><a href="https://www.dropbox.com/s/e1mpwlqeu2k9kyb/signed.pdf?dl=0" rel="nofollow noreferrer">Working signature</a></li>
  </ul>