Abstract: A method of imposition proofing of printing data of a document onto a set of proof sheets is described, the document having one or more sections, each proof sheet having a recto side and a verso side, the printing data including imposing information and printing information for positioning and printing a set of pages onto one or more print sheets, each print sheet having two print sheet sides, a verso print sheet side and a recto print sheet side, each print sheet side having at least four pages. The method includes, for each print sheet in the printing data, dividing the pages imposed on each side of the print sheet into printer spreads of two pages, and determining information referencing the printing data, for defining how each printer spread is printed on each side of a proof sheet.