The document has been altered or corrupted since the Signature was applied

I get "Document has been altered or corrupted since it was signed" when signing with:

PKCS #12 cert for document signing and we do timestamp.

I am using  JSIGNPDF version 1.6.4 for signing as well as for timestamping and for validation using Adobe Reader 11. In JSIGNPDF we have option to change properties of document like  "no changes allowed" or "no filling allowed", etc.

When we enable this option and sign our pdf we get the above metioned error while on the other hand when we disable it the signature validates correctly.   

So, request you to help me out here.