A digital signature or ID is more commonly known as a digital certificate. Digital IDs help to validate your identity, and they can be used to sign important documents including PowerPoint presentations. As far as PowerPoint is concerned, a digital certificate is necessary for a digital signature because it provides the key that can be associated with a digital signature. Digital certificates make it possible for digital signatures to be used as a way to authenticate digital information. In this tutorial we will show you how to add a digital signature in PowerPoint 2010.