1. An image forming apparatus comprising: a manuscript reader that reads image data from a manuscript a printing unit that prints the image data read by the manuscript reader on printing paper according to set printing conditions, and a controller that controls the manuscript reader and the printing unit, wherein the controller functions as: a character extracting unit that extracts characters from each of a plurality of different locations in the image data, a line width judgment unit that compares line widths of the characters that were extracted by the character extracting unit, determines whether or not there is a difference in the line widths of the extracted characters, determines, when there is the difference in the line widths of the characters extracted, that the manuscript is pencil writing, and determines, when there is not the difference in the line widths of the characters extracted, that the manuscript is not pencil writing, and a printing-condition-setting change unit that, when the line width judgment unit determines that the manuscript is pencil writing, changes the printing conditions to printing conditions for pencil writing for performing image processing of pencil writing, and causes the printing unit to print the read image data on printing paper according to the changed printing conditions for pencil writing.