When using Verdocs, signers apply an electronic signature to each document. Once the document has been signed by all recipients, Verdocs applies their Digital Signature Certificate, certified by Entrust, which seals the document. Since the certificate is issued by Entrust and applied to your document by Verdocs, any modern PDF viewer can check to see if the document has been modified and remove the modification. If a digital signature is applied without an authorized certification it is unverified and may not be legally binding or secure.