Whenever you add weight to the racquet it adds swingweight. A given amount of lead placed at the butt cap will add the least swing weight while that same amount placed at the top of the hoop will add the most swing weight.
The only way to reduce a frame's swingweight is to remove weight from the racquet (not easy to do). You can trim the bumper or you can go to a grip that weighs less.
As a side note, don't confuse static weight and swingweight. Static weight is the weight of the racquet when placed on a scale. Swingweight is measured on an RDC machine. Just b/c a frame has a light static weight it doesn;t mean that it has a low swingweight.
People use a frame's swingweight measurement to get a rough idea of how hard it is to swing that racquet fast. Frames with lower swingweights are easier to swing fast.