Abstract: In a high volume printing and packaging operation, stationery is fed by document feeder 10 to a laser printer 14. The printer prints both text and discrete identification code on the page both text and code being supplied from a system controller 16. The document is then folded by folder 22 and the code read. Enclosures are added as dictated by the code and the code read again prior to insertion in an envelope by inserter 24. A correct code verification causes an ink-jet printer 26 to print the name and address on the envelope. The marking code comprises a series of small marks normally unnoticeable to the normal observer and each representing a digit, whose value depends on the position of the mark on a notional circle whose center is a fixed distance from a pair of reference marks.