Edits are allowed for usage within your project. You aren't allowed to share or sell the edited assets.
I'm ok with you handing the files to a commissioned artist for them to work with those files. They aren't allowed to use the art assets (original or edited) on their own project (they'd need to buy their own license for that) and are not allowed to sell the edits they made as an asset pack, to other clients, or in whichever other way. ;3