Fix download link in docs

docs/source/index.rst

@@ -47,11 +47,6 @@ the pip tool. See :ref:`a_started` for more details.
 * PyPi Project: https://pypi.org/project/novelWriter
 * Social Media: https://fosstodon.org/@novelwriter
 
-.. toctree::
-   :hidden:
-
-   Main Page <self>
-
 .. toctree::
    :maxdepth: 1
    :caption: Introduction

docs/source/usage_projectformat.rst

@@ -29,7 +29,8 @@ applicable.
 
    **For Developers**
 
-   A full description of the current file format is available in the `File Format Spec 1.5`_
+   A full description of the current file format is available in the
+   :download:`File Format Spec 1.5 <fileformatspec15.pdf>`
    document, available as a PDF. This document is intended for contributors to novelWriter, those
    building project conversion tools, either to or from tne novelWriter format, and for those who
    wish to make their own templating system.