If there's anyone out there that forges ledgers -- or used to do it until you took an arrow to the knee...How do you do it? Does it effect prices?

You only do them for Thieves Guild jobs. It doesn't do anything otherwise.

They're only for jobs.

They don't affect anything, it is just Thieve's guild side quests.

Edit: Didn't see @Kothre post.

Thanks. I wondered about that, but there seems to be a lot of them.