1. An image processing device, comprising: a receiving section that receives a print job from an image processing terminal though a network, the print job including a page layout to be printed; an extracting section that extracts a line image to be warned from the page layout based on a threshold value of a line width specified by a user; and a warning section that warns, under a condition that the extracting section extracts the line image, so that a user recognizes that the line image is included in the page layout.