Deleting a file will not permanently delete it, only move it to a deleted folder.
You can always recover deleted documents later if you need to. To do this:
Click on the 'Deleted' option in the folders list to the left of your files list.
Tick the file/s you wish to recover.
Click 'Restore File'.
Confirm you wish to recover the selected file/s.
The recovered files will then be moved back to the Files page.