def add_double_page(writer, page_size, print_page):
    """ Adds a double page """
    width, height = page_size
    page = writer.insertBlankPage(width=width, height=height, index=writer.
        getNumPages())
    l_page = print_page.left.page
    if l_page is not None:
        page.mergePage(l_page)
    r_page = print_page.right.page
    if r_page is not None:
        page.mergeTranslatedPage(r_page, width / 2, 0)
