Do paintball's hurt if you have on armor?

Yes, paintballs will always hurt, if you cannot feel them under your clothes, you are technically cheating.

Although it hurts to get hit with a paintball, you can't wear extra padding because the point is for the paintball to break. Experienced players feel the paintball much less because they are accustomed to the pain. If your adrenaline is pumping really fast during the game, you are likely to not feel the shot too much.