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...
I'm pretty sure that was not done. If the faxes were sent via computer, TrueType "hinting" would have avoided aliasing problems without creating the weird artifacts observed on the fax. And since such artifacts would only have been created at the first fax generation, I'm pretty sure the documents weren't faxed directly from a computer.