Scribd is a publishing service that allows a person to quickly and easily share writing on the web by either attaching documents to the wordpress site or embedding them within the page.
To do use a Scribd shortcode a person needs a scribd account(which is free). The website for getting an account is here: http://www.scribd.com/. Once an account is made all a person has to do to is upload whatever pdf or word document you want to insert onto you page onto scribd, then click embedded docs and then the wordpress button to get the code that you can paste into the wordpress blog to inset that document onto the page.
The results looks something like this:
For a more detailed explination see:http://en.support.wordpress.com/scribd/