An automatic duplicating system in which computer fanfold documents are fed by an automatic handling apparatus having a tractor and drive means for advancing the document across the platen of the processor for the system. An arrangement is provided which will control operation of the processor and the automatic handling apparatus in order to acquire duplex copies of the simplex document. The arrangement includes circuitry and controls which advances the document in a manner wherein a copy of every other frame section is diverted to a holding station and then returned to be reprocessed on its underside with the image of the succeeding frame section.