FileBase is a very useful WordPress plugin to organize thousands of your media files in the media library. It is similar to wordpress categories like in the posts. It allows you to create an individual and unlimited folder structure in the WordPress media library view.
The best of this plugin is that the native WordPress media management system is used to organize all of your existing media files like Images, Audios and PDFs.
If you buy, you get: Forever FREE updates and high quality and fast support.