I don't know if it's a known manner or not, but here is it: Some people can be pickpocketed but when you steal them (i.e. take from their inventory), they become angry, not matter if you are invisible. So, I opened a container and drag the containt of his pocket in the container, he doesn't consider it as a steal. Then I pick the goods in the container (WARNING: If they see you picking the objects stolen, even in the container, they will consider that you steal them).
I also found a bug with George: If you pickpocket his money more than 1 time, you got the money and his money double, then raise of 1.