It's a module specifically designed to help you manually remove documents you have uploaded and linked to your site.

A change made to Drupal in the last year by the Drupal Community of developers removed the ability to delete files via the existing method in preparation for the rollout of the Media Library Initiative. The problem stems from the fact that the Media Library is still in development and not ready for use. In the meantime, we're offering this interim solution.

Unless you are deleting an entire page permanently, as described in the Deleting Pages write-up, it is strongly recommended that you do NOT delete any documents or files you have associated with your page. Why? Because your page's Revision history relies on the existence of the files in order to maintain an active, accurate list of Revision points to which you can roll back your page if needed.

Deleting pages in Drupal is permanent. We have methods for recovery, but it's better to act as though you might someday want it back rather than delete the content outright.

Once a content node is created you have a couple of ways to delete it:

Even if you're convinced you'll never need the content again, consider Archiving it instead as an insurance policy.