I have 2 toilets that when you flush them paper comes back up. It seems there is not enough suction. I have used drain cleaner and I do not have a septic tank.
Thanks for you advice.

Likely low-flow toilets. And it's not suction, it's pressure. Possibly the house has low water-pressure (the equipment is not working properly) or it is not fully turned on. I'm not experienced completely on the topic but have run into the problem before. Check the dials on the machine in your basement.

First, are both the toilets on the same floor of the house? Just a guess, if both are going down slow, and or leaving paper in the bowl, it could be the jets under the bowl rim are blocked. And the siphon jet in the bottom of the bowl is blocked. If so, you will need to clean jets on bowl rim with end of coat hanger, the jet in the bottom of the bowl if there is one, I cleaned them with my pocket knife. Hope this helps.

Plumber 21 years, now selling real estate.

Hey Jabez... start at the basics. How old are the toilets? Do your toilets have a siphon jet (a hole opposite the toilet drain hole in bowl)? If you lift the lid of toilet tank does the 1/4" flexible tube from your fill valve connect and/or flow into the overflow tube (at center) and feed water into toilet bowl? Also, do the holes under the toilet bowl rim flow freely?

You want to check these things first... then check to see if original parts in toilet... sometimes people replace parts with wrong parts.. and then both toilets have issues.

If siphon jet present... glove up and stick finger in hole and unplug the hole in each unit. If rim holes clogged, a coat hanger can be used to unplug these... if wrong flappers in place, then replace. IT is all about hang time with flappers.. if wrong flapper.. wrong hang time, simply will not work right.

Last resort.. get us name and model number of toilet (under tank lid engraved/stamped inside tank lid or tank) and we will see what else we can find out.