The Pendulum Whiteboard Printer is a fully-automatic robotic device for marking or otherwise effecting whiteboards, pinboards, or other vertical surfaces. The physical device consists of an effector platform suspended by two suspension wires whose lengths are adjusted by motorized spindles mounted above and on either side of the board surface. The position of the effector platform is adjusted by winding and unwinding the wires. Methods are provided for using the Pendulum Whiteboard Printer to perform various actions and for moving the effector platform to a desired location.