The home was built in the 40's and has original pipes. There are water lines in place for the tub (although pressure is a little low-kitchen & bathroom sinks' flow is fine) and I would like to add a pipe for a shower head. There was one that was attached to the tub faucet but it was useless except for a drizzle.
The pipes are accessible from the wall behind because it is the linen closet. Should this be left to a professional? Could the faucets be to blame for the lower water flow to the tub?
I'd appreciate any advice. Thanks so much!

Have you removed the shower head and checked the flow? Let me know, Tom,