Individuals with foot drop caused by stroke or cerebral palsy (CP) have a particular need for robotic ankle exoskeleton. This paper proposes an untethered soft robot using an origami actuator to lift the toes of the wearer. The weight, connections, and complex control of the system are reduced through mechanical design. A compact and portable pneumatic system is designed to perform suction and compression with a single pump. The load test of the actuator shows the capability of 300N in 30 kPa. An untethered, simple and affordable robotic ankle exoskeleton is developed with the pneumatic actuator. The wearer can finish its simple 3-step donning procedure within 1 min.