No, you can carefully paint interior doors while on the hinges. While it may seem easier you will have to be extra careful when painting for best results. Taking the door off its hinges before painting offers a smoother process and better access, especially for larger doors. However, painting the door while hung is feasible with careful preparation using painter's tape and wedging it open slightly. Consider convenience, space, skill level, and the number of doors. Both methods can work well, but removing the door allows for a more manageable painting experience and better results.