PURPOSE: To be able to operate a document forming apparatus after stopping rapidly on the basis of a predetermined instruction by displaying the stopped reason on an LCD when the apparatus is stopped on the way of printing to recognize the reason by an operator.

CONSTITUTION: When a printing stop is designated, a method of designating a printing comment comprises transmission of an input, when a line modifying key of a keyboard 1 is depressed, through an input controller 2 to an editing function unit 4, to display a message on an LCD 8. An operator who observes the message, selects an item of an object, and presses a selection/execution key to store the result by the unit 4 in a line modifying data table 7. Printing stop information input by the key is stored in the table, and a printing comment designation is stored in a document buffer. When the printing stop designation information exists in the line modification during printing, the content of next line is displayed on the LCD 8, and when the displayed printing guide message is designated, the guide message is inversely displayed, and controlled so as not to print the guide message.