Abstract: A sheet processing apparatus, for example for flexographic printing and die-cutting of corrugated paperboard container blanks, has first and second successive processing sections connected by a transfer section. The sheets are successively passed through the various sections in positional registrations therewith. A sensor senses a sheet while in the transfer section and provides a signal representative of the positional registration of the sheet in the transfer section. A computer system determines from the signal whether the sheet would enter the second section in correct positional registration for processing by the second section, and adjusts as necessary the positional registration of the sheet while in the transfer section to cause the sheet to enter the second section in correct positional registration therewith.