Manufacturers typically assign individual print limits to their offers to make sure everyone gets a chance to print their coupons. Most coupons have a print limit of one or two.
http://help.coupons.com/articles/76-Why-did-I-get-a-Print-Limit-Reached-message-when-the-coupon-never-printed
http://www.today.com/id/44493132/ns/today-today_news/t/extreme-couponing-sparks-backlash/#.UhNYP9J32So
http://www.salon.com/2011/04/05/extreme_couponing_tlc_premiere/
Extreme couponing no matter how you look at it is way out of control. Some have even been deemed as 'coupon scammers' but according to those articles, retailers only have coupons to give everyone a chance to try out the product. Coupons are not there to save people money and they certainly can't be used for mass purchasing. If you don't have a problem using mass quantities of coupons at your store, expect it down the road since this is a continuous problem. I believe our store had banned excessive couponers but i don't really know since i don't cashier much, and i really hate to cashier because of this. Read up a little more on why extreme couponing isn't really the best, especially when you are attempting to get more then your fair share of an item with that particular coupon. Our store even had a major problem when consumers bought the items with the coupons, they would then return the items at the original cost.
Don't get me wrong though, i like your idea and passion in helping out the homeless but everybody including the manufactures are dealing with this where only 10% are actually using the coupons but the reason the coupons are there, like i said before and in that quote it's there for everyone, not just for a few people which is why more manufactures are going towards the digital coupon method so they have a better way of making sure everyone has a chance at trying out a particular product.
I highly suggest you look for another way, one that isn't so controversial or illegal. You could try scanning the coupon and print it out that way, but if the codes on them are different (which is most likely what manufactures are doing now) you might not be able to do it that way either. It's really not worth the effort because for one you hold up the lines, especially in stores where cashiers have to make sure what they are scanning is accurate and valid so even if you could print out 100 copies you would still most likely get grief at the register due to the associate pointing out that one or 2 coupons is the limit.