Add link to NumPy PDF docs

Author: yashasvimisra2798

doc/source/_templates/indexcontent.html

@@ -6,8 +6,8 @@
 {% block body %}
 <h1>{{ docstitle|e }}</h1>
 <p>
-  Welcome! This is the documentation for NumPy {{ release|e }}
-  {%- if last_updated %}, last updated {{ last_updated|e }}{% endif %}.
+  Welcome! This is the documentation for NumPy {{ release|e }} 
+  {%- if last_updated %}, last updated {{ last_updated|e }}{% endif %}. For a PDF version of the documentation, go to https://numpy.org/doc/.
 </p>
 <p><strong>For users:</strong></p>
 <table class="contentstable" align="center"><tr>