this is going to be an indirect answer, but I just find reading pdf files on the Aura a pain. If you are not averse to fiddling around with your ereader, I'd install Koreader - that is excellent for pdf files (and more) and relatively straightforward to install, if you are patient enough and follow
the instructions (I am no techie, I can guarantee that, and managed nonetheless).
Patience and attention are important if you are not technically minded (like me) as putting the .tgz files in the wrong place may bric your device. If you are a techie, it'll take you five minutes, I am sure.