This patch enables building .pdf documentation using new 'pdf-docs'
tox environment. The newly created tox environment creates latex
source codes using sphinx-build and then builds the pdf
documentation using make.
Also, this patch makes minor changes in the documentation source
code to make sure that the .pdf and .html documentation looks
good.
Story: 2006070
Task: 35454
Change-Id: I74a151163812a3dc8fde9f85739882a54ad11fd3
4a02a8411d