在一张纸上打印两张PDF，无需缩放

I have a pdf document which covers half of an A4 page. Is there a way to duplicate the text/images of that document, such that I get a single page A4 document (pdf file) with twice the orginal content, one above each other? Since the original only covers half a page, no scaling should be necessary.I have a pdf document which covers half of an A