I'm a little confused? Why would it be desirable to download books in PDF format. I guess, from what I've been reading here, my Nook and NookColor do that but why would I want to? Is there a benefit?
And to the people asking about free books. Books that are in the public domain (copyright expired, if I understand correctly) are available for free or at a nominal price. I think on the Nooks where you search for books and have the option of putting in a price range for your search, you put
0.00. Somebody already mentioned the Free Fridays.
And some asked how to download library books. I'm sure it depends on what program your library uses if there is more than one. But the library staff should be able to tell you what to do. My library doesn't have theirs up and running yet, but I have volunterred to be a "super-user" to help the patrons with learning how to use it.