I've had a number of documented boats. In Wisc, if documented, you don't need to put numbers on the boat, just the two stickers on the lowest part of the visible transom. Same in California.
For more expensive boats, there is a clear record of title when documented. For smaller boats, probably not worth the effort. But whe buying an expensive one, a current clear document is more or less clear title to the boat.
PV is documented. My 42 Carver and my 28 Carver were documented. My Glaspar, Barron, Zoom, and Jetskis are not.