PDF Documents created using DynamicPDF can have digital signatures or digital certifications added to the document. Digital signing and digital certifying are both ways to approve the current document with a digital ID (or digital signature). In both signing and certifying the document, applying the digital ID verifies that you (the owner of that digital ID) are signing off on the document. Any changes to the document after a digital signature is applied will invalidate the signature and be noted. Certifying a document (versus signing it) allows the owner of the digital ID to specify certain changes, if any, that a user can make. We will get into more detail on both of these in the topics below.