E-Ink Kindles can technically display PDFs, but in practical terms, you wouldn't want to read a PDF book on one. Unless the PDF dimensions are just perfect (and it rarely ever happens, maybe the DX is better?) or you generated the PDF yourself, a PDF's typical page margin gets rendered, generally cropping off the text on the bottom and/or right hand side of the page. This means that you have to pan the PDF page back to a near-center position every page turn. It's disruptive to your reading flow.