Originally Posted by pholy
In brief, a PDF file is designed for display on a certain sized 'page' - typically A4 or letter size for business office documents, or possibly 6x9 inches for a book. But one of my readers has a 5" screen (3x4), and the rest are 6" diagonal. None of the available PDF rendering software does a good job of zooming, panning, or cropping, and the programming required to try does use more power, than a simple mobi or epub file.
I agree with what you say if you are trying to get the pdf to reflow. However, if the pdf for the reader is formatted to the page size (screen size) of the reader, then the output is perfect. The higher end pdf programs like Adobe Acrobat will allow you to make any custom page (screen) size.