Java facebook error validating verification code
For more information about signature warnings and valid and invalid signatures, see the Each time a document is signed using a certificate, a signed version of the PDF at that time is saved with the PDF.
Each version is saved as append-only and the original cannot be modified.
Acrobat provides users with the capability to add a document timestamp to a PDF without also requiring an identity-based signature. (See Configure a timestamp server.) A timestamp assures the authenticity and existence of a document at a particular time.
Verification details are listed beneath each signature and can be viewed by expanding the signature. This feature analyzes the document for content that may alter the appearance of the document.
It then suppresses that content, allowing you to view and sign the document in a static and secure state.
Some states are called when a user alters the PDF-signed content.
In contrast, XML signatures only have two data verification states, valid and invalid.
When you receive a signed document, you may want to validate its signature(s) to verify the signer and the signed content.