Obviously the transfer agent bears the lion's share of blame here, but 'lack of printer' feels a bit helpless. It's hard to imagine that a scan of a wet signature on a printed email would be more valid than print-to-PDF and 'Add Signature' in Preview in one's own hand, or that the transfer agent would even be able to verify. One could even go the extra mile with ImageMagick[0] if they were so inclined.
Obligatory IANAL, this is not legal advice, and it's probably at least technically wrong.
Millenials, I mean "people without printers" (to be inclusive), can all go to Fedex or a public library and print it out and scan it there. You can also take a picture with your smartphone, I've seen lawyers be more anal about the signature than about the scanning part.
Obligatory IANAL, this is not legal advice, and it's probably at least technically wrong.
[0]: https://tex.stackexchange.com/questions/94523/simulate-a-sca...