To manufacture a plate-making file including a page having a specific magnification by specifying magnification of a specific page of a file and extracting its data, and multiplying the value of the page size of the specified page, the values of the coordinates and sizes of characters, and the values of the line width and line length of ruled lines by respectively specified magnifications.

A generation system for a print data file loads various print block application programs on a large-sized computer such as a workstation and input data 10 of a basic plate-making layout file are generated by input from various databases, manual input, etc. To a data converting device 20 as a file editing device for printing, the input data 10 of the file are inputted to enlarge the layout, characters, and ruled lines of a desired page, thereby generating print data 30 in the form of a plate-making file. This file is inputted to a printing-out machine 40 to prepare an art work 50.