I can attest to the same. I've signed security contracts with government agencies by taking their PDF, opening in in Apple Preview and attaching image of my sig

I can attest to the same. I've signed security contracts with government agencies by taking their PDF, opening in in Apple Preview and attaching image of my signature, and sending back. Same with Xournal in Linux. This is how real world, big money contracts get signed. The email history probably attests more to the bonofides of the document than the document itself. It's up to the signers to spot differences visually. Another tactic is contracts signed by another authorizing action like "your check is as good as your signature language" or "Under the U.S. Uniform Electronic Transactions Act (UETA), this Agreement is executed electronically when both parties agree via e-mail, an Internet web page, or other electronic means and the Client pays the deposit as set forth in..." A simple email saying I agree is acceptable under US law. No cryptographic PDF features necessary.