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.
You can use a combination of pdfjam and pdftk to do this:
pdfjam --offset '0mm -148.5mm' half-a4.pdf --outfile other-a4.pdf pdftk half-a4.pdf stamp other-a4.pdf output double.pdf
pdfjam is being used to shift the page down half a page (A4 = 297mm tall, and 297÷2=148.5). If you need to shift the other way, you'd use
Then pdftk puts the two pages on top of each other.