unfortunately the kindle 2 does not natively support .PDF's. they can be used but only through conversion either using amazons service, a third party program (i use
calibre), or
savory. thats why i said it would be nice if .PDF's could be cleanly converted to another format.
having said that, i did check out "the art of war" and converted it using calibre into .MOBI. to me it seemed to turn out pretty well compared to the .PDF however there was some formating loss.
you can see here that while it is converted there are some problems. but as far as resizing text i think that the kindle does a good job. when dealing with .PDF's it not text size its actually converting while keeping the formating that is the problem that you will run into