A method for producing proof data for a blank of a package in an electronic reproduction system for packages includes linking CAD data from a CAD system and graphic data from a graphic system to form blank data, and using the blank data in a sheet assembly system to produce printing data describing a printed sheet. From a blank of the finished assembled printed sheet, proof data for output in a proof system is derived, the proof data containing all the changes to the graphic data of the blank that have been made in the sheet assembly system. The proof data can describe a two-dimensional or three-dimensional proof.