Possibility to add custom fields to files

It would be great if you could develop an extension or other solution to add custom fields to files.

For instance, for a reference library, I would like to add and display the following fields:

1. Title
   
2. Author (not the WP-author, but author of the original file)
   
3. Year (year of publication)
   
4. Hyperlink (to the source where the document was found)
   
5. Document (the download)
   

By default, only a 'Title' and 'Description' can be added right now.