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.