The best tool to convert between different ebook formats is Calibre (http://calibre-ebook.com) - sometimes it does a good job on PDFs, other times not so much. But that is the nature of PDF - it's hard to extract content in a way that reflects the original document. What I've done to get a PDF file on my Kindle is to first export the content as MS Word using Adobe Acrobat, and then use that Word file as input to Calibre to create e.g. a MOBI file that I can read on my Kindle.
BTW: The iPad supports PDF ebooks.
Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...