A printer driver for generating print job data to be transferred to a printer in response to a drawing instruction determines, based on combining condition, whether the received drawing instruction can be combined with another drawing instruction. If the printer driver determines that the received drawing instruction can be combined, the printer driver stores the received drawing instruction as intermediate data. If the printer driver determines that the received drawing instruction cannot be combined, the printer driver combines intermediate data of already stored drawing instructions into a single item of print job data and outputs the print job data to the printer. The combining condition is that the received drawing instruction meets all of three conditions.