A print control system adapted to control a digital printer having a first machine-readable ink of a first colour and a second ink that is not machine readable at the same wavelength as said first ink and that is of substantially the same colour, said system being adapted to control said printer to print upon a document in said first ink a position—determining pattern readable by a digital pen to enable said pen to acquire data to enable a position of said pen in said pattern to be determined, and to print human discernable content that is not read by said pen superposed with said pattern using said second ink and not said first ink.