My media is not being protected.

My concern is protecting the media I have available for download and that the link only work for the member that that link is meant for.
I have downloads that I have placed in the media section. Some of the downloads are intended for subscribers of specific membership levels. I use the permlinks on a page that list the downloads (see code below for that page) available to that group.
When that person is logged in and they click on the link to open the download, it comes up in acrobat and the actual url is displayed. For one, the permalink that I have set it to is not displayed. Secondly, now the user has this link, can give it to anyone else and someone who is not even logged in has access to this page. I have assigned the media I am to protect to the protected groups listed below and yet the url is not changing when the user opens up a file from my media list.
Am I doing something wrong, or is the program not functioning correctly?