Now I'm understanding what you're asking for.
The goal of this free ebook offer is to increase the number of people subscribed to the blog.
From the first part:
The free ebook landing page is made with a static Wordpress Page. You enter the subscribe form on the Thank you page will be the link for the free ebook. The subscribe form is an RSS to your email feature that is inside Feedburner. They'll give you the code to drop this into any page you want to get folks signed up for email updates from your RSS feed.
The second portion is called placing a footer/signature in your RSS feed.
Here's a good rundown of the kinds of things you can put at the end of your posts.
Add a Footer to Your RSS Feed: 7 Practical Examples
Your friend links to the free report as his footer message in his feed. There are a few wordpress plugins that will do this for you. Take a look at:
WordPress › RSS Footer « WordPress Plugins,
WordPress › Ozh' Better Feed « WordPress Plugins
Does that help explain how what your friend is doing that you too can do?