A sheet folder apparatus for use with a web-fed printing press includes upstream and downstream folding assemblies and a conveyor for delivering cross-folded sheets from the upstream assembly to the downstream assembly. A head stop is positioned within the delivery path defined by the conveyor for limiting the movement of the cross-folded sheet along the path and for positioning the sheet relative to the downstream folding assembly. The position of the head stop along the delivery path may be adjusted during operation of the apparatus so that it is not necessary to shut the apparatus down to make adjustments to accommodate various signature size and format changes in the apparatus. A registration system is also included for registering the two folding assemblies relative to the apparatus when either the upstream assembly is replaced or the downstream assembly is enabled.