Not sure at all about PDF files... I'd check App World for some PDF readers and check out the reviews before you pick one to try.
As for true e-books, I have a Barnes & Noble Nook, and as such, I've learned that B&N offers a FREE Nook Reader App for all of the leading smartphones. The only catch is BlackBerries... they no longer mention it on their
Nook Reader Apps Page, because they have apparently stopped updating the Nook App for BB. You have to go to bn.com from your BB's Browser, and if it's available for your model, you'll get a download link. If it isn't, you'll be SOL. But if you can get your hands on it for your BB, it should work for all e-book formats supported by the Nook.