add link to Asciidoctor PDF docs in navbar

Author: mojavelinux

src/partials/header-content.hbs

@@ -46,9 +46,7 @@
           <div class="navbar-link">Extensions</div>
           <div class="navbar-dropdown">
             <div class="navbar-item">Add-on Converters</div>
-            {{!--
-            <a class="navbar-item" href="{{{relativize (resolvePageURL 'pdf-converter::index.adoc')}}}">PDF</a>
-            --}}
+            <a class="navbar-item" href="{{{relativize (resolvePageURL 'pdf-converter::index.adoc')}}}">PDF <small>Ruby</small></a>
             <a class="navbar-item" href="{{{relativize (resolvePageURL 'reveal.js-converter::index.adoc')}}}">reveal.js <small>Ruby, JavaScript</small></a>
             <a class="navbar-item" href="{{{relativize (resolvePageURL 'epub3-converter::index.adoc')}}}">EPUB3 <small>Ruby</small></a>
             <hr class="navbar-divider">