There are converters available from Amazon and/or Mobi for pdf and doc files.
Amazon can do a lot of money only from selling kindle, like Apple does with the iPod.
Granted the PDF converter seems to have some trouble with graphics PDF's, but for books the converter works very well.
Hacker Igor Skochinsky used DRM to load Mobipocket books onto his Kindle. Using a series of scripts, he's able to convert eBook files to Amazon's AZW format and then add the necessary serial number DRM, specialized per an individual's particular Kindle.
A revolutionary portable reader that wirelessly downloads books, newspapers, magazines and blogs to a crisp, high-resolution electronic paper display that looks and reads like real paper, even in bright sunlight.