Might I suggest looking into using iText for batch converting PDF files to N800 format? I looked into it and it seems fairly simple. It's in java 1.4 so it should even be possible to run on the N800. Alternatively somebody could set it up as a web service like MaemoTube. I will look into it once I get my N800 - which should be within a week! Woohoo :-)

Check out http://itextdocs.lowagie.com/tutorial/ for limited, but very application oriented docs.