The deciding factor here is the board itself. Two people can certainly ride on a paddleboard, much the same as two people can share the same bicycle seat. However, out on the open water, things can be a bit trickier, and several factors could indeed affect your overall experience or even your safety. Always consider the size and weight ratings of the board before venturing out. The paddleboard should be properly rated to withstand at least the full weight of both riders.