Image forming apparatus with creaser control, control method thereof, printing system, and non-transitory computer-readable medium

A printing system comprising:

• an image forming unit configured to form an image on a sheet;
• a creasing unit configured to crease the sheet conveyed from the image forming unit and comprising a creasing die which is selectively attachable, wherein the creasing unit creases the sheet by pressing the creasing die against the sheet;
• a setting unit configured to set a plurality of creasing positions on the sheet to be creased by the creasing unit, the setting unit being configured to independently set, for each creasing position, whether to crease from a front surface on the sheet or crease from a back surface on the sheet;
• and
• a control unit configured to:
• (i) check a setting of the plurality of creasing positions to determine whether creasing from both surfaces for the sheet is to be performed,
• (ii) obtain information of the creasing unit to determine whether the creasing unit is able to crease from both surfaces of one sheet, and
• (iii) if it is determined that creasing to both surfaces is to be performed and it is determined that the creasing unit is not able to crease from both surfaces of one sheet, display a warning screen on a display unit to prompt a user to change the setting of the plurality of creasing positions.