Revert all leading /2009 from URL Patters since this is now handled in Apache on server.
{% extends "base.html" %}
{% block title %}Preview of the paper{% endblock %}
{% block content %}
<h1>Preview of the paper</h1>
<a href="{{ out_path }}/paper{{ paper_id }}.pdf">
<img src="{{ out_path }}/paper{{ paper_id }}.png"></img>
</a>
{% endblock content %}