Whole house furnace humidifer install…

Fuck, this dry heat is killing my throat, skin, and paint (in places). So I am getting an Aprilaire Humidifier installed at the furnace, whole house style. I figured a humidifier would install on the supply duct to get maximum benefit, but the dude doing it says the unit sits on the return air duct. I’m no contractor, but it seems humidifying air (return side duct) then running it through my gas furnace would dry out the air. I didn’t want to sound like a simp and argue, but does a whole house furnace humidifier really sit on the return air duct, which is right close to the furnace?

Also, how does the humidity stay at 30-40% if it runs through the house’s ductwork? Would I have to run the fan more to get humidified air in here or will the humidifer’s thermostat actually kick on the fan to hit the set rate % of humidity if it’s being met? I hope this thing is the solution because I feel like I am in a sauna, but I don’t feel "warm". Thanks to all you guys who are smarter than I.
Flow-through humidifiers may be mounted to the air return duct and connect to the hot air supply off the furnace by using a humidifier supply takeoff duct
The supply takeoff bypass duct diverts some heated air to the humidifier by taking advantage of a natural pressure differential between the supply and return sides of the furnace. The warm air absorbs moisture from the evaporator pad inside the humidifier and returns to the warm air stream through the cold air return duct and furnace.

Traditionally in commercial building humidification is achieved by heating the air up hot, adding humidity then cooling it to the desired temperature. In heating season it just doesn’t cool it.

I would be very consernsed with him putting it in the return because you are now drawing moisture through the fan, which won’t help. Also, you have to be cautious of mold growing in the duct.
i was just thinking of getting a aprilaire humidifier myself..

I’m getting this one

with this for my thermostat

I just put a tin can of water on my wood stove to keep the air moist. but i guess that might not work for central air.