You could probably use a Folder Action, but yes, I used Hazel. If you search for Hazel in the search box at the bottom of this page, you’ll find some posts where I discuss ways I use it. The most detailed post was this one: https://www.40tech.com/2012/07/01/the-worlds-easiest-most-awesome-hands-off-set-and-forget-paperless-filing-system-mac/