PDF Doc Viewer not working

I am working with a modified theme. Currently it uses the image annotation plugin along with a javascript image zoom on the items/show.php page. However, over the course of my edits, my Omeka site no longer displays pdf files in the docs viewer. An older version of this modified theme still displays pdf files in the docs viewer.

I've tried a conditional statement: `<?php
if (item_fullsize())
echo image_annotation_display_annotated_image_gallery_for_item();
echo display_files_for_item();

But that doesn't seem to do the trick, it just gives me a link to the file.

Any thoughts as to where I may have stopped this functionality would be greatly appreciated.

After some searching on the site (http://omeka.org/codex/Plugins/DocsViewer) I added `<?php
if (class_exists('DocsViewerPlugin')):
$docsViewer = new DocsViewerPlugin;
?>` before my conditional statement above, and it seems to have done the trick.