The pressure reducing valve can be adjusted, but you should probably check a few things first. has there been a bunch of new homes put up since you moved in? If so, you may have had high pressure once, but no longer do. You could have a clog in the valve or the water meter or supply pipe (I assume that you don't have a well, as you wouldn't need a reduction valve if you did). You can buy a pressure gauge and put it on a faucet designed for a hose. That would give you an idea of what you really have. If you have a friendly neighbor, you could attach it to their house and see if their pressure is much different than yours. Is this an old house (you might have said, I forgot)? If so, then it may have a galvanized supply line, even if your interior piping is (now?) copper. Has there been any construction around you around the time you noticed the pressure dropped? Normally, the pipes are burried deep enough where construction equipment don't hurt them (unless they are digging!), but it could happen. I don't know what happens if a pressure reduction valve fails. It might restrict flow. Do you have a whole-house filter system, or a water softener? either of these could cause restrictions. Maybe the most obvious question, has someone recently turned the main water supply valve off? Maybe they didn't turn it all the way on!
Some pros will probably have some other, maybe more obvious things for you to check.