In this paper we show that pneumatic stepper motors for MR safe robots can be constructed using rapid prototyping techniques such as 3-D printing and laser-cutting. The designs are lightweight, completely metal-free and fully customizable. Besides MR safe robotic systems, other potential applications include high-voltage switchgear and nuclear power plant systems which also restrict electric actuation. In addition, it can be applied to other actuation systems where pressurized air is available and lightweight, rapid prototypeable actuators are needed. Five pneumatically-driven linear and rotational stepper motors have been developed with forces up to 330 N, torques up to 3.7 Nm, stepping frequency up to 320 Hz, dimensions ranging from 25 mm to 80 mm, free of backlash and power up to 26 W. All five motors are constructed from six 3-D printed parts and four seals, held together by nylon screws or clips. The described stepper motors outperform state-of-the-art plastic pneumatic stepper motor designs, both in specifications and in manufacturability.