If you just need to link it for download, you can do that in the files section and then hyperlink to the file on the public page –http://nationbuilder.com/how_can_i_link_to_a_stored_file_on_my_pages 

If you are trying to display a PDF map, you can post it on a PDF display software like Scribd, then post the URL (not hyperlinked) to the PDF display in your content editor – the Embed.ly integration in NationBuilder will convert the URL to a display.