You can get the Overdrive app to get library books straight to your Nook.
Can Adobe Reader be installed on my SD card so I can transfer books directly to my Nook instead of to my PC?
If you root your NC with ManualNooter 5.08.20, you can use Adobe Reader, Documents to Go, and other apps to read your pdf files.
In addition, you could use Dropbox to share files between your devices. For example, you could drop a copy of The State of the Union.pdf file into a Dropbox folder and read it from your NC or pc.