Do you know the dimensions of the text blocks of the SSRN articles, roughly?
The Nook's screen is probably a bit small to read these comfortably, and it sounds like conversion likely won't work too well. Still, there are steps you can take to make this kind of PDF more readable. I list a number of options in
this blog post: reading PDFs on portables – soPDF and BRISS are probably especially important.
Ones that are big enough to read such PDFs comfortably without tools such as these are more money, obviously.