I’m not an expert either, but the pressure regulators I’ve seen are for making sure that the pressure doesn’t exceed X amount and reducing it if it does. If you want to increase pressure (my problem), you need a pump. Most people have a pressure regulator in their home (typically required by code) to make sure if you suddenly see a pressure surge from the water company it doesn’t blow up the plumbing and appliances in your house. Some of us (like myself) really wish it could increase water pressure so I wouldn’t have to whine to the city about my lackluster culinary water pressure (I have issues with both culinary and secondary(irrigation)).
Water pressure is essentially a form of potential energy given there are devices that can turn pressure into electrical energy – so it makes sense if you’re pressure is too low that you’ll need a device that turns electrical energy into mechanical energy (an electric pump) to get the pressure back up.