It's interesting that the problem they had was with the signature. You can very easily make a handwritten signature on an iPad. I don't see how there's any practical way to tell the difference between a high-quality, handwritten signature done on an iPad with either a finger or an Apple Pencil and a scanned signature done with a pen.
Are you sure that's not just some excuse they gave you?
Interestingly, there are LaTeX packages for coffee stains[1] and to simulate the variability of an actual typewriter[2]. I suppose both of these involve discrete objects (the coffee stain, individual characters) and photocopy/scan effects involve 'fuzzing' of the whole image, rather than any particular element, and TeX isn't really set up for the former.
It's interesting that the problem they had was with the signature. You can very easily make a handwritten signature on an iPad. I don't see how there's any practical way to tell the difference between a high-quality, handwritten signature done on an iPad with either a finger or an Apple Pencil and a scanned signature done with a pen.
Are you sure that's not just some excuse they gave you?