I am a little confused at what your trying to do, but I have an idea if I am on the correct path.
You want clients/customers to click on these links in the Specials.tpl to take them to pdfs?
If so, make a copy of your PDF and put it into the images folder.
So that would be xcart/images/something.pdf
Now when you type our <li> put the full path to your pdf file.
<li><a href="http://www.YOURWEBSITE.com/xcart/images/somthing.pdf"</a></li>
If you xcart installation is on your root, then you can omit the folder xcart and just have "http://www.website.com/images/something.pdg"
The possible reason why you are thrown to the admin page is because the PDF is located admin section?
If you want something to be public, I wouldn't put it in the admin folder.
Hope this helps.