A two dimensional pattern design for secure documents serves as both a machine readable code and an aesthetic part of the documents' design. A method for generating the design generates a variable auxiliary message comprising message values and maps the message values to a two dimensional pattern of areas on the document. The areas each comprise an arrangement of pixels on the printed document. Depending on a value of the message mapped to a corresponding area, the method assigns a visible structure to the corresponding area. Different visible structures are assignable to a single value of the message to create a visible design having a desired aesthetic appearance.