An image forming apparatus to function as an input unit configured to input image data, a printing unit configured to print an image based on the image data input by the input unit, a control unit configured to perform control to, if the image forming apparatus operates in a first mode, print by the printing unit an image generated from the image data input by the input unit, and if the image forming apparatus operates in a second mode, print by the printing unit an image obtained by adding a predetermined pattern image to the image generated from the image data input by the input unit, and an accepting unit configured to, if the image forming apparatus operates in the second mode, accept selection regarding whether to perform printing in the second mode in response to operation performed to start printing the image.