i have been reading books and im trying to get my pets to 500 and its around 366 right now

Wanted to amend my answer, because I saw the thread where you were looking for the highest paying pet job. The intelligence requirements for that one are steep, so you might need those boosters after all. I still say that books are faster, though.

Anyway, here is a list of some items that boost intelligence when used on your pet. Some of them boost other stats as well, you can click on each item to see exactly what their effects are. Good luck!

Reading books pretty much is the fastest way to boost pet intelligence. There are stat booster items out there that give intelligence too, but for the most part they're either super expensive, hard to come by, or both.

If 500 is all you need, just stick with the books. I wouldn't get into boosters unless you plan to do any serious battling.