Acrobat User Community Forums

Hi,

I'm doing a basic survey about *PDF security*.

As part of my survey on PDF security, I read in the following document (www.adobe.com/products/acrobat/pdfs/Ado … yGuide.pdf)
that when Adobe certifies a document as valid, this means that Adobe has done *a bit-for-bit comparison* of the document as it was at the time of signing against the document as it was at the time of the validation check, and it has found these two versions to be identical.

I wonder how Adobe performs this *bit-for-bit comparison*! Does Adobe keep the original document all the time (say in a centralized server) and compare it to the version being viewed by users? This doesn't sound to me as a practical technique.


Would you provide me with some explanation in this regard (i.e.
*bit-for-bit comparison in PDF documents*)? A link to some white papers or technical reports would be also very useful.

Thanks in advance.