Folding method and folding device and document processing system

A method for generating a folding instruction for orthogonal folding of a stack of sheets into a document, the method comprising the steps of, for each sheet of the stack of sheets:

• a) receiving an orthogonal folding action on the sheet defined by a fold type, an orientation relative to an observer, the fold type selected out of a mountain fold right, a mountain fold left, a mountain fold bottom, a mountain fold top, a valley fold right, a valley fold left, a valley fold bottom and a valley fold top;
• b) generating at least one function having the orthogonal folding action and the sheet as input, and at least one ordered list of new sheets with an orientation relative to the observer of each new sheet of the at least one ordered list of new sheets as output;
• c) repeatedly applying steps a) and b) to each new sheet of the at least one ordered list of new sheets until the sheets in the last applied steps a) and b) form the document;
• and
• generating a folding instruction comprising a concatenation of the at least one generated function on the stack of sheets, the folding instruction intended to be transmitted to a folding device for orthogonal folding of the stack of sheets into the document,
• wherein the orthogonal folding action on the sheet is also defined by a distance of an edge of the sheet to a fold line intended to be created by the orthogonal folding action, and wherein the sheets that form the document have at least two different sizes.