Abstract: In a booklet binding machine a flat cover signature is added in leading edge register to a single or collated signatures moving in a travel path prior to saddle folding. The signatures are passed as a unit to a stitching station to be jogged and center stitched. Overlapping pairs of arbor mounted rotary slitting blades at opposing sides of the travel path head and tail trim the signatures during its movement by feed rollers between the pairs of slitting blades. The uppermost arbor and blades are angularly rotated at a greater speed than the lowermost blades to insure a clean cut of the signatures. Cooperating presser rings on the arbors cooperate with the slitting blades prevent buckling of the signatures and strip tail-out of the trimmed edges thereof. Bearings mounting the uppermost presser rings on the upper arbor allow the uppermost rings to rotate at the rate of travel of the lowermost rings.