Abstract: Multiple simultaneous envelope duplicating apparatus has a windowed feed elevator supplying envelope stacks to an offset duplicator. The elevator has an open frame supporting a pair of spaced apart parallel envelope stack supporting plates. The plates and the frame define windows for receiving in vertically movable relationship, guide members to maintain the envelope stacks upright and in alignment with suction feet at a receiving station of the offset duplicator. A delivery end of the duplicator having a receding stacker also has an open frame supporting a pair of spaced apart envelope stack supporting plates to receive printed envelopes, and define windows for receiving in vertically movable relationship, a second set of guide members to maintain the printed envelope stacks upright. Upright member supporting bases are adjustable so that the guide members can be fitted to bound the sides of different sized envelopes. Bulk envelope chargers have envelope receiving side plates and a back retaining plate.