Forgery is something that is seen in Third Edition. I think it would be neat to have a way to apply this to the game. Perhaps if players could make seals with signet rings, then people could forge such a seal to make the note look as if it were genuine to someone else. It would make for some very interesting roleplay.
I would see it as a trade rather than a skill because it is something that takes a lot of work to do when done in a very precise manner, and it is hard to pull off good forgeries (unless the person has no idea what the seal looks like in the first place.) It would also explain more IC reasons for trusted messengers to carry things around, interception of notes and the likes. I just see immense opportunities with RP here.
Paxos