1. A system comprising: a memory that stores requirements for sequencing each of multiple activities available at a print shop into workflows; a Graphical User Interface (GUI) operable to graphically present a workflow comprising an ordered subset of the activities to perform for processing a print job, to graphically present the available activities, and to enable a user to drag the available activities onto the workflow to alter the workflow; and a processing system operable to detect an activity being dragged by a user, to determine locations in the workflow where requirements for the activity are met, and to operate the GUI to highlight the determined locations.