right from the
ebook reader matrix the 600 can support BBeB (LRF/LRX), PDF, EPUB, TXT, RTF, JPG, BMP, GIF, PNG, MP3, AAC natively.
if you're looking for conversion software i strongly recommend
calibre which also has a
forum here as well. you will be able to convert pdf's to epub (commonly used on the 600 and other ereaders) but the results may not be acceptable.
calibre is free to download and use, you can try it out now on some of your documents and try to preview what they might look like on an ereader display.