How I can add an "e-mail a free ebook" created on my website as a promotion?

I am a writer Articles for the rehabilitation of addicts and books. I build my own website and how to insert a nice link that allows visitors to my site website to send a free ebook with a friend may have an addiction. I understand that this is a great way to promote my site.

Create your own eBook PDF to insert a link to your website. Make sure you say that people can go in this ebook so you do not change the content, if you encrypt the e-book pdf you can not change the text. Make sure you have a link on its website, which links the two. Hope this helps