A printing control apparatus includes a conveying unit that conveys a document to a reading unit, a detection unit that detects a size of the document before it begins to be conveyed, a detection unit that detects the size of the document after the document begins to be conveyed, and a control unit that performs a copy job using the reading unit and printing unit based on the size of the document detected before it is conveyed in a case where the printing unit starts to print the image data before the reading unit finishes generating image data for one page and performs a copy job based on the size of the document detected after it begins to be conveyed in a case where the printing unit starts to print the image data after the reading unit finishes generating image data for at least one page.