Kindles can read a variety of non-proprietary, non-DRM'ed formats. They read TXT, HTML, JPEG, and non-DRM Mobi files directly.
Use Mobipocket software to convert PDFs to that format so you can read them on Kindle.
How do you load other eBooks onto the Kindle? Just add Amazon DRM.
Hack let you convert encrypted Mobipocket files that were intended for another reader so that that work on 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.