OK, I have been using the Amazon Kindle DX for nearly two months and I’d grade the general ability to read and work with PDFs on the device a C-.
Yes, the device natively supports PDF documents – this means you can just attach the Kindle DX to a PC and drag and drop the PDF into the Kindle’s document folder and it becomes available as soon as you eject the usb device from the PC. You can also email the document to the Kindle DX, the point being is that it does not have to go through ANY translation in order to be displayable on the Kindle DX (native support).
A common mis-conception related to PDF documents is that they are all the same. As an oversimplification, one can generally scan an existing paper-based document into a PDF format in one of two ways – the easiest scans the document as an image or a picture that is displayable as a PDF; the second is to actually encode the text into the document. The Kindle DX treats only text PDF as searchable, as the image is, by definition a picture of the text and therefore cannot be searched. Now if you are starting in the digital realm, I would recommend outputting information to a Microsoft Word document, which, after translation, is much more useable on the Kindle DX.
The biggest disappointment I have found is that font size cannot be changed in a PDF document on the Kindle DX. This was one of the features that I was looking forward to, but the text you start with is the text you end up with – no changing font sizes the same way you can with a word document or a book. Landscape mode helps a little in most instances, but then messes up alignment and page breaks. Curiously, the scrolling option also does not exist, which could help alleviate some of the alignment issues – you can only change a one page at a time.
Things aren’t all bad – most PDF documents are faithfully recreated on the Kindle DX screen – the real problem is that for technical documents and magazines with a bigger starting footprint, the text is fairly small, and not being able to increase font size seems like the missing link to increased useability. Perhaps a firmware update is in the Whispernet?