I wanted to do something similar. I'm initially using the plugin to maintain and display a set of documents to site visitors. I'm using the documents shortcode to pull documents by category.
Since the users are not familiar with the documents themselves, I wanted to add a short description to each document so that the user didn't have to open each one to figure out what it was. I wanted a single description for each document, so using the revision description didn't seem like the right idea. I didn't see a a general description field defined (I may have missed it), so I created a custom field with the key "Description" and the description as the value.
Recklessly taking my life into my hands, and voiding my warranty for the plugin, I found the function documents_shortcode section defining the Documents shortcode in the plugin's wp-document-revisions/includes/front-end.php file.
I added the following lines to the loop that displays the list of documents found:
<?php echo get_post_meta($document->ID,$cf_key,TRUE); ?>
(I had previously defined $cf_key = "Description" above the loop.)
Amazingly, it worked as intended and the shortcode now displays a list of documents, with each document link followed by the description.
I presume I could have duplicated the entire shortcode code and given it a new name had I wanted to leave the original shortcode available.