Well, graphics certainly add to the Mb of the file. But I've yet to see a truly 'unwieldy' PDF. Even the Pathfinder RPG Core rulebook, at over 550 pages and lots of graphics, which comes in at almost 80 Mb is still usable enough for me that I'll have it up on the laptop while running/playing. It does slow down a little when transitioning pages, but not enough to call it a problem.