This title of Assassin's Creed II doesn't include classical cheat codes support. There is no console window or any other similar imput, where you can enter the "magic" word and get the corresponding option activated. That's how they developed the game, and there's no future update which will add this feature.
Almost every PC gaming site out there will actually offer Assassin's Creed 2 cheats, but instead of traditional list of codes, they will give you a bunch of tips and tricks on how to unlock various features and archivements (the most stupid and uselles thing).
The word CHEATS, in this kind of video game industry, stands for unlimited health (god mode), stamina, weapons, armor, items, and similar goodies and it should stay that way.
If you want to enable real cheating for Assassin's Creed II, go and get yourself a good trainer within the TRAINERS link on our site.