Generate and publish a PDF version as well

Change-Id: I913a998b3a382ae87b1e90182127f4d201980a98
diff --git a/conf.py b/conf.py
index 9537807..ee23c50 100644
--- a/conf.py
+++ b/conf.py
@@ -65,3 +65,11 @@
 
 pygments_style = 'tango'
 pygments_dark_style = 'material'
+
+
+# -- Options for LaTeX output ------------------------------------------------
+# https://www.sphinx-doc.org/en/master/usage/configuration.html#options-for-latex-output
+
+latex_documents = [
+    ('index', 'ndn-packet-spec.tex', project, author, 'manual')
+]