Allow the ability to paste images (in particular a signature)
It would be nice to have the ability to paste in my signature on a PDF. You also might consider storing the signature graphics under user profiles.
I would appreciate a feature to upload and insert a signature when needed.
The convenience of this idea has also a downside -- if electronic documents having your signature somehow end up in others hands who you don't trust, it could easily be used to forge your signature / for identity theft.