The same shims that adjust camber on the upper control arm also adjust caster. It depends on how you use them, for instance, take an 1/8" from the front to rear bolt and it would adjust caster up about 1 degree. Removing or adding shims equally front and rear will only change camber, any other differance will adjust caster. Just think of the upper arm 2 mounting point at the frame than the upper ball joint as a triangle. moving around the 2 points at the frame will move the ball joint forward or rearward. Or inward or outward, depending on what you do with the shims.
Hope that makes sense .