I see the poster above with the funny name, beat me to it and posted while I was typing my post. Anyway here it is:
The Watchtower has 32 pages for the same reason that the diameter of NASA’s solid booster rockets are based on the measurement, four feet eight and a half inches. (4 ft 8.5 inches.)
This measurement is based on the width of two horses asses from the Roman Empire times.
Check it out here if you do not believe me:
http://www.utilitech-services.com/jokes.html
Now the number of pages in the Watchtower magazine is based on how the magazine is made. It is made from sheets of paper, 14 inches by 9 inches. Each of these sheets are printed on both sides, and they are folded in half in the magazine. That means each piece of paper makes four printed pages of the Watchtower. The total number of pages in the WT must always be a multiple of four. It cannot be an odd number nor a number not divisable by four.
Now the fact it is 32 pages probably depends on the way printing presses print them.
Perhaps Randy Waters could give us more info on how the printing press works and has some idea why the choice is 32 pages, not 24 or 40.
belbab