We want to use PDF approval forms with digital signature approval. However, we noticed that PDF forms can still be modified by the first approver even after the second approver approved:
1) The form is filled in and signed electronically by one person.
2) All fields are looked and content cannot be changed.
3) Second person signs electronically and sends back the approved document to the first approver. (so that he can forward it to the next approver or pass it on to the processor)
4) However, The first approver can remove his digital signature, change the content and sign electronically again.
How to prevent that after the second approver signed electronically that the first person that signed electronically cannot change the document? It seems that Acrobat cannot prevent this. Is there any other option?
(We know that PDF has a change record for the document to see what changes were performed after the document was signed. However, this does not help if approved forms are printed. By this, the first approver can commit fraud.)
If the second approver is the last person who signs this document he can lock his signature. After that no changes to the document are permitted. It is more complicated if there are more than two people signing. Only the last signer can lock his signature since signature locking disables ability to sign again.