What do you mean by pdf download link? Do you want a link that will download a PDF or do you want a link to download Adobe Reader? It's not clear.
If you really just want to put a PDF file download on your website, you just use a normal
<a href=... tag into the HTML (with the href link pointing to your uploaded PDF file).
If you want to add a link to download Adobe Reader to your website, see http://www.adobe.com/misc/linking.html