Proper way to work with contractors/freelancers?

For example, let’s say I bought some sound effects from Audio Jungle. However they’re not 100% ready-to-use for my game. So I’d like to hire an SFX artist to modify/remix them.

My problem is… can I do that? How to do it properly? From the licnese:

You can modify or manipulate an Item, or combine the Item with other works, to suit your End Product.

You can’t redistribute the Item as stock, in a tool or template, or with source files.

Is it “redistributing” to send the files to the artist that I hired…? So I can’t hire someone else to edit them?