While professionals don’t recommend using PVA as a sealant before painting, some people have found success in doing so. If you can afford to get your hands on a good quality primer that is recommended by the manufacturer of the floor paint you are going to use, you definitely should. If you use the wrong type of primer or PVA, you run the risk of lifting and peeling paint which is difficult to remove without starting again from scratch.
There is some debate as to whether sealing a concrete floor with PVA is a good idea. It’s true that any splashes that go outside the floor, such as on the walls will be problematic when applying emulsion paint or that the sealer will go tacky and sticky when applying adhesive. You can find PVA at your local hardware store or DIY store.