This module allows you not only to link a pdf file, that is somehting you do not need a module for, but to embed the file. The main advantage of this is that your PDF file will instantly show when the page loads.
This is a huge advantage an can really make a difference. Embedding is easy, you only have 3 options, the width and height in px or %, and the pdf file you want to embed.
To embed simply publish the module and add it to your content or to a module position.