You can adjust the pressure valve on the pump to increase water pressure but it you are not a plumber I would suggest hiring one.
You can up the water pressure by adjusting the pressure switch. A 40 psi switch should have a cut in pressure of 20 psi. Inside the cap of the pressure switch will tell you how to turn the adjusting nuts to raise the pressure. But you should know that if you raise the pressure too much you could cause the plumbing to leak.
By the way, what is the pressure valve Gwynnyth is talking about?
Gwynnyth the forest wench is correct. At the pump there a switch box, remove the cover and you see the Adjusting Screw. IF, you not know much about this hire someone, or go to a hardware store and have them explain how it work. It be good if there a pressure gage so you know how high you turn it.