After installing this plugin, I found that the include tag does not work in the theme templates and can only be pasted into posts. The functionality was exactly what I was looking for (download/view), but I wanted it on all my posts -- and -- I did not want to email pdf like the other plugin I found.
Anyway, I created a really simple work-around for this in case anyone is interested. Just put the following code into your template where you want the pdf link to appear. I put mine in the meta section of the 'single post' template, so that the icon appears in the meta of those pages.
<a href="<?php bloginfo('url');?>/wp-content/plugins/post2pdf/generate.php?post=<?php the_ID();?>">
<img src="<?php bloginfo('url');?>/wp-content/plugins/post2pdf/icon/pdf.png"></a>
The above example shows only a clickable pdf icon (I removed the text).