A method of processing a substrate web into individual sheets for the production of security documents, such as banknotes, the method comprising the following steps: a) providing a substrate web; b) inspecting the substrate web to check a quality thereof; c) cutting the substrate web into individual sheets; inspecting the individual sheets thereafter to check a quality of the cutting; d) sorting the individual sheets in dependence of results of the inspection at step b) and c) to produce at least two types of sorted sheets (S A, S B, S C), including good sheets (S A) meeting desired quality requirements and bad sheets (S B, S C) that are found to exhibit defects; sorting the bad sheets (S B, S C) into (i) partly-defective sheets (S B) that are found to exhibit only minor defects and that are partly usable for production of security documents and (ii) entirely-defective sheets (S C) that are found to exhibit major defects and that are not adequate for production of security documents; and e) processing at least the good sheets (S A), and preferably also the bad sheets (S B, S C), into individual stacks or reams (R, R W) each consisting of a predetermined number of individual sheets, wherein the good sheets (S A) are processed at step e) into grade-A stacks or reams that are intended for production of security documents, wherein the partly-defective sheets (S B) are processed at step e) into grade-B stacks or reams that are either intended for production of security documents or for print job preparation or make-ready purposes, and wherein the entirely-defective sheets (S C) are processed at step e) into grade-C stacks or reams that are only intended for print job preparation or make-ready purposes. a) providing a substrate web; b) inspecting the substrate web to check a quality thereof; c) cutting the substrate web into individual sheets; inspecting the individual sheets thereafter to check a quality of the cutting; d) sorting the individual sheets in dependence of results of the inspection at step b) and c) to produce at least two types of sorted sheets (S A, S B, S C), including good sheets (S A) meeting desired quality requirements and bad sheets (S B, S C) that are found to exhibit defects; sorting the bad sheets (S B, S C) into (i) partly-defective sheets (S B) that are found to exhibit only minor defects and that are partly usable for production of security documents and (ii) entirely-defective sheets (S C) that are found to exhibit major defects and that are not adequate for production of security documents; and e) processing at least the good sheets (S A), and preferably also the bad sheets (S B, S C), into individual stacks or reams (R, R W) each consisting of a predetermined number of individual sheets, wherein the good sheets (S A) are processed at step e) into grade-A stacks or reams that are intended for production of security documents, wherein the partly-defective sheets (S B) are processed at step e) into grade-B stacks or reams that are either intended for production of security documents or for print job preparation or make-ready purposes, and wherein the entirely-defective sheets (S C) are processed at step e) into grade-C stacks or reams that are only intended for print job preparation or make-ready purposes.