ive heard that pitchers should do more pull exercises than push. what are some good pull exercises?
Not sure where you heard that, but its not correct. For any athlete you want to maintain balance between push and pull, or antagonistic muscles. There are circumstances where athletes have unaddressed imbalances that need to be corrected through doing more of a certain type of exercise.
As for pull exercises, there are lots. Basically, they are all variations of rows, cleans, deadlifts, and snatches.
Maybe this is in reference to there being 3 muscle groups to accelerate the arm and only 2 muscle groups to decelerate the arm. And deceleration happens in less time than acceleraton. Whenever I have pitchers do band work, I have them do more sets for the back side than the front. This is the recommendation of the NPA.