A print document conversion apparatus includes plural software-based conversion units and a controller. The plural software-based conversion units perform a software-based conversion process for converting print document data described in a page description language into page image data having a bitmap image format. Each of the software-based conversion units requests a hardware-based image processing apparatus to execute specific image processing in the software-based conversion process, and generates the page image data including a result of the specific image processing in response to the request. The controller activates an additional software-based conversion unit that performs the software-based conversion process when there is a possibility that a state where at least one of the software-based conversion units waits for the hardware-based image processing apparatus to complete the image processing occurs. The controller controls the number of additional software-based conversion units not to exceed a predetermined upper limit.