The PC side Connect Software has some capabilities to add bookmarks too -- I haven't played with this much. It may be possible to connect your Reader, and add a mark (to the copy on the Reader) in the Connect software and have that show up on the Reader.
Another alternative that comes to mind is to figure out what font size you like best and convert your text to a PDF sized for the Reader's screen, then you could be reading equal sized pages on both platforms. Of course, you'd be reading really small pages on your PC screen....
I suppose you could also read on your PC via the Connect software ... that might be simplest.
