None of those ways would introduce some of the specific types of distortion that are present in the documents. They were clearly faxed, and I'd like to see a pixel-perfect sample of a real page sent from that Kinko's to see if the first-generation fax was produced there.
The .pdf files will have all of the distortions of the fax machine plus the distortions of the scanner CBS used to produce the .pdf files.
Of course the other possibility is that they were faxed directly from a computer...