title: Signed PDF showing message "The validity of the document is unknown", iText
body: <p>I am using iText to apply digital signatures in PDF. The digitally signed PDF is showing message like "the validity of the document certification is unknown. The author could not be verified.At least one signature has problems." at the top.</p>
  
  <p>When I add the certificate to my trust identities which is used to create signed PDF, then the generated signed PDF shows "Signed and all signatures are valid". </p>
  
  <p>Is it possible to fix this by without adding certificate to trusted identities? </p>
  
  <p>Thanks in advance.</p>