A PDF reader (such as Adobe Acrobat Reader) can verify the validity of an electronic signature. When the document is opened, the PDF reader automatically performs two operations:
It calculates the document’s fingerprint to see if it matches the fingerprint of the document that was signed;It checks the digital certificate to ensure its validity (therefore the authentication of the signatories).
If the reader recognizes one of these elements as invalid, a message will warn the user that the electronic signature is invalid. This removes the need to initial the document on each page.