Use Mobipocket software to convert PDFs to that format so you can read them on Kindle.
The Kindle only allows the reading of Amazon DRM-protected content.
DRM is not to prevent other files from being readable on the Kindle.
Kindles can read a variety of non-proprietary, non-DRM'ed formats. They read TXT, HTML, JPEG, and non-DRM Mobi files directly.
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.