3. A printing system comprising: a printing mechanism for effecting printing along a printing path extending in a predetermined direction; means for positioning a first document in a first printing zone extending transversely across the printing path; means for positioning a second document in a second printing zone overlying the first printing zone and extending beyond the first printing zone in the predetermined direction; document sensing means positioned within the second printing zone adjacent to the first printing zone and on opposite sides of the printing path for detecting the presence of a document in the second printing zone; and means responsive to the document sensing means for selectively advancing either a first document through the first printing zone or a second document through the second printing zone.
3. A printing system comprising: a printing mechanism for effecting printing along a printing path extending in a predetermined direction; means for positioning a first document in a first printing zone extending transversely across the printing path; means for positioning a second document in a second printing zone overlying the first printing zone and extending beyond the first printing zone in the predetermined direction; document sensing means positioned within the second printing zone adjacent to the first printing zone and on opposite sides of the printing path for detecting the presence of a document in the second printing zone; and means responsive to the document sensing means for selectively advancing either a first document through the first printing zone or a second document through the second printing zone. 6. The printing system according to claim 3 wherein the document sensing means includes at least one lever having a portion extending into the path of a document positioned in the second printing zone and responsive to the positioning of a document in the second printing zone for generating a predetermined output.