Well, sort of...a clipping mask is a mask that can hide part of something, and show what you want to show. So like what you said but the clipping mask defines the visible portion.
Some clipping masks might just be the printable edge or boundaries of a document. Other clipping masks might “cut” something out of the background to allow you to overlay it on something else.
Sometimes a PDF will actually create a clipping mask out of something, depending on your origin art. Then when you open it(the editable pdf) in another program like Illustrator, you can release the clipping mask and it’s way different than what you started with.
But to get back to the beginning- what should have happened with Dear Leader’s BC is they scan (image scan) the original document. period, end of story. You can then put the image in a pdf for distribution purposes, but it would still be a flat image no matter what.
The people at these agencies aren’t going to get all fancy with the scanning. There are 2 types of bureaucratic scanning. There’s scanning for information (digitizing documents) when it would be OCR scanning, and then there is scanning for document archiving (image scans of original documents). In the latter case you aren’t going to OCR when you are digitally archiving originals that may have peculiarities or be historical. That would be like going to ancestry.com and someone OCR the Ellis Island documents. Extreme example but you see what I mean.
Don’t feel you have to soft peddle if I’m wrong. I enjoyed reading your post...and being corrected. I love this type of discussion thread and What counts is of course the right answer.