Signing a PDF on the iPad, then adding a digital signature

Hello,

I'd like to create a form (in, say, Acrobat XI) and distribute it to salespeople travelling. I want them to fill out the fields, and have the customer sign on screen. This all works great -- question is, can they then digitally sign the document somehow, so both them and the client have a digitally signed copy, rather than just a PDF each side can claim is fake?

Thanks,

-- D