The kindle native supports Amazon's proprietary format AZW, PDF, TXT, unprotected MOBI/PRC. Audio: AAX, AA, MP3.
Amazon converts PDF, HTML, DOC (Word), RTF, JPEG, GIF, PNG, BMP, MOBI, PRC to their AZW format.
So in regard to PDF you should be fine with the Kindle. For a nice review about the Kindle DXG take a look here -->http://www.the-ebook-reader.com/kindle-dx.html
The same should apply to the new Kindle 3 only that it is smaller than the Kindle DX of course.