But which PDF should it be?

PDF letter for U.S.? PDF A4 for the rest of us? PDF for Kindle? Kindle DX?

no matter which one you choose, someone will be unhappy with it... some of these devices do _not_ let you zoom in or zoom out, so the .pdf has to be right-sized from the get-go, or it's a no-go. so you have to let the user specify; see how feedbooks.com does it... of course, there is the alternative of giving 'em a tool that lets _them_ generate the output .pdf according to the dimensions that they've specified, which can entail more than pagesize. including things like block-paragraph vs. indented, curly quotes vs. straight, choice of font, choice of font-size, choice of leading, background color, and any number of other variables... or, you know, you can try to put _all_ of the options in your web-converter. -bowerbird