For PDF's the Nook Simple Touch and Glowlight has basic reflow which works well with single column text only PDFs. It has 6 font sizes to pick from and sizes 2 or 3 are more than adequate to read, in fact 3 is a bit big. This YT video explains it well in the first few minutes.
http://www.youtube.com/watch?v=ayAcdHuI5hw