"Or it's because he had access to the original paper copy of the document and just scanned it himself."

Absolutely! This is why we are safer with only electronic copies of documents (but properly protected). The same argument applies to credit cards and SSNs. They are vulnerable (and hard to keep secret/private) precisely because they are accessible in their original form. Check what our resident expert in security Leo Reyzin says about this http://www.bu.edu/today/world/2007/09/16/safety-numbers

"Or maybe he never had any original document and it was a vindictive forgery."

Sure, but here again the answer is to use the proper technology that can check authenticity of digital content.

The issue is not that we don't know how to solve some (if not most) of the challenges posed by the pervasiveness of the Internet, the issue is that we as a society are not demanding the necessary changes to allow the deployment of such solutions.

--Azer