A downloadable pdf is a link. To make a pdf document available for download, add it to the media library. As with images added to the media library, the pdf document will be assigned a URL. Copy this URL and use it as a link.
For example, if you wish to make a newsletter downloadable in a pdf format, save the newsletter as a pdf file, drop the pdf file into the media library, and copy the resulting link. Enter the name of the newsletter to your text and add the URL as a link to the text on the page.