I guess you dont need anything magical for that... It would have to be made possible that parchments can be eddited more than once. Perhaps only addative? "contracts" dont have to be a game feature, but parchments that allow such actions would open up the posibilities for players to make their own contracts and perhaps even ledgers?
Edit: (added a bit about my views on this)
I really like maps/books/messages... the more players can do with them the more uses players will find for them, from deaththreats to wanted posters to taxes and a farms inventory. I think the game should provide the tools but the players should find their own aplication of those features.