I converted a two-columns pdf book of 144 pages (that is really a 288 pages book) using papercrop. It went up from one meg to 18 megs.
On Linux, I used imagemagick to batch reduce the size of the images by 50"percent to get about a 6 or 7 megs file but divided in 144 numbered fragments. I declared it to be a png file and it processed the whole lot.-mogrify -resize 50% *.jpg-
After that, grouping all this in a zip file and converting to lrf with comic2lrf. This is a lot of work, on two platforms...but the result is readable and not too heavy.