A duplexing image forming device which selectively directs printed pages back onto the original paper supply, flipped over with respect to the page's original position and swapping the leading edge for the trailing edge, for printing on a second side. The formatter in the image forming device then instructs the printer engine to print the second side of the page and reverses the order of data supplied to the print engine. A paper diverter is installed at the output of the fuser mechanism in the print engine. The diverter selectively diverts paper from the standard output path into a vertical gravity reversing slot through three reversing rollers. The paper is fed from the diverter up through the nip between the single driven reversing roller and an idler reversing roller. The driven reversing roller pushes the paper up into the vertical gravity reversing slot. As the trailing edge of the paper exits the nip between the driven reversing roller and the first idler roller, the trailing edge is carried by the driven reversing roller up and over that roller into the nip between the second idler reversing roller and the driven reversing roller. The driven reversing roller then forces the new leading edge of the paper through a duplexing channel where a duplex paper drive mechanism directs the paper onto the top of the existing paper supply tray.