title: pdf signature requires validation vs signature has problems
body: <p>Anybody, please explain what's the difference between signatures.
  When i open one PDF document - Adobe Acrobat 9 shows the message "At least one signature has problems" but if i open the other PDF then the message is "At least one signature requires validating".
  Seems like both PDFs were signed by self-signed certificates, but the messages are not the same.
  This difference is extremely significant for our business.
  Please help.</p>