Probably not worth the money, try iBooks from apple first

It loads PDFs easily and seems to have minimal lag. The main problem is changing pages. Sometimes the next page is off center (as in, only the bottom left quarter of the page is showing) and turning pages is difficult. I just discovered iBooks from apple and I think it works better! Also, it doesnt remember the last thing you viewed when you open it the next time

Turbotj about The Fastest PDF Reader