Adhesions themselves are painless, but they can lead to pain in two ways. Since they can’t stretch they can pull on the gut when it moves, and that can hurt. They can also cause the gut to kink or twist a bit, which can narrow the opening. If food or liquid get caught behind the narrowed opening the trapped material will increase the pressure inside the gut, which hurts like heck.
Adhesions are very, very common after abdominal surgery (they occur 93% of the time). Most of them don’t cause any trouble at all.