The mdp object provides support for Modify
Detection Prevention Plus (MDP+) digital signatures. Acrobat 8.0
and later supports MDP+ digital signature for XFA-based forms.
In Designer, MDP+ signatures are implemented with a Signature
Field. Signature fields enable you to specify a collection of form
objects that are protected by the document signature. Using document
signatures prevents the form or a portion of the form from being
modified.