Which users have access to use the plugin to set permissions?

By default Administrators and Shop Managers can use the plugin.

You can give access to this plugin to other users by editing their WordPress' user roles capabilities.
Required capabilities to use:
‘mak_wc_download_permissions’
‘edit_product’
‘edit_products’
Optional:
‘edit_private_products’
‘edit_published_products’
‘edit_others_products’