Merge pull request realpython#375 from eet6646/master

Issue realpython#361 - Link to PDF

Author: sigmavirus24

docs/_templates/sidebarintro.html

@@ -31,4 +31,5 @@ <h3>Useful Links</h3>
   <li><a href="http://python-guide.org/">The Guide Website</a></li>
   <li><a href="http://github.com/kennethreitz/python-guide">The Guide @ GitHub</a></li>
   <li><a href="http://github.com/kennethreitz/python-guide/issues">Issue Tracker</a></li>
+  <li><a href="https://media.readthedocs.org/pdf/python-guide/latest/python-guide.pdf">The Guide as a PDF</a></li>
 </ul>