First off, do you know if your pump is capable of delivering higher pressure by setting a higher setting on your pressure switch?
Typically it's a 20 psi differential setting, such as 40-60 or 50 to 70 psi. Where the pressure is allowed to drop to say 40 psi before pump comes on and it builds the pressure up to say 60 psi, where it would shut of.
So does you pump come on at 40 or shuts off at 40?
Then comes the question of what comes next in your piping system? Do you have any type of filter/water softener system that would cause additional pressure loss?
Checking your pressure further along down stream(in the direction of the flow) could be done easily with a hose end connection pressure gauge. That would give you a better indication of what your actually getting for pressure further along.
Checking pressure on the first and/or the second floor would be even better to help determine where losses may be occurring.
Piping size contributes to pressure loss but not as big a factor as other possibilities.
You should understand that pressure loss takes place with flow. The higher the flow the higher the pressure loss.
And then of course, as you know, pressure loss occurs based on the height it is raised above the source. Referred to as Elevation Head. One foot of elev. head = 0.433 psi or 1 psi - 2.31 feet of head.
So in the case of going from the Basement to the second floor, if it was a say 16 foot elevation change the pressure loss just from height difference would be 16 x 0.433 = about 7 psi. And that's not flowing. Once it starts flowing the additional pressure loss would be based friction loss through the pipes.
I would suggest you take it a step at a time to try to determine where the biggest losses may be occurring. We know that pipe size makes the difference but that's not where you want to start making changes, as many think.
Feel free to ask any question at all. I can help guide you through.
It wouldn't hurt to start collecting pieces of information as you go. Like size of main pipe. Where reductions in pipe size take place as you follow the piping system. Is it a single family or multiple. Number and probability of simultaneous uses is a big factor, although it may not be in your case.