Illustrations of human movements are used to communicate ideas and convey instructions in many domains, but creating them is time-consuming and requires skill. We introduce DemoDraw, a multi-modal approach to generate these illustrations as the user physically demonstrates the movements. In a Demonstration Interface, DemoDraw segments speech and 3D joint motion into a sequence of motion segments, each characterized by a key pose and salient joint trajectories. Based on this sequence, a series of illustrations is automatically generated using a stylistically rendered 3D avatar annotated with arrows to convey movements. During demonstration, the user can navigate using speech and amend or re-perform motions if needed. Once a suitable sequence of steps has been created, a Refinement Interface enables fine control of visualization parameters. In a three-part evaluation, we validate the effectiveness of the generated illustrations and the usability of DemoDraw. Our results show 4 to 7-step illustrations can be created in 5 or 10 minutes on average.