Can I sell someone else's digital products?

Site URL: https://www.firain.com/

I hope someone can point me in the right direction. 

A client has created an online magazine. She wants to sell it through online shops as a digital download. I am struggling to find information on any issues that might arise from selling a digital download on behalf of someone else, as a product in your shop. 

Has anyone had experience with this method of selling an digital download?

Thanks, Jo