I have a well and a pressure tank, current pressure at top of holding tank is 38 lbs. Well cuts on at 40 lbs and shuts off at 50lbs. My problem is that when more than one facet, shower, or toilet is flushed the water pressure at the facet or showers drops in half, sometimes more. What do I need to do so that I can maintain pressure with more than one fixture drawing water?

How old is your home and what material are your pipes made of? This sounds like a volume problem rather then a pressure one. Volume and pressure. A system must have both to operate correctly. The problem with rusty pipes isn't a pressure problem, it's a volume one. Let's say you have 50 PSI at the pump and a 3/4" galvanized service that has built up rust that chokes it down to 3/8".
You will still have 50 PSI when you open a faucet, but, flush a toilet or open another faucet that calls for more volume to feed the extra demand and the pressure fails. I believe this is what's happening to you. All the pressure in the world isn't going to help if you don't have the volume to back it up. If this is the case adding more pressure isn't going to help. A repipe job is just about the only solution. Good luck. Tom

What happens reading do you get on the pressure gauge 30 seconds after opening faucet of flushing toilet? How big is your tank and is it a blatter tank?

For speedball1, I used your solution for a similar problem, adjusted the square-D box cut-in and cut-off pressures. I measured and adjusted the pressure in the bladder tank and set it a the correct 2 PSI lower than the cut-in pressure. Now all is much better.
For the pipes, copper about 12 years old.
For hkstroud, badder tank is 4 years old and 30 gallon capacity.