Can customers download invoices for their payments?

Yes they can!

Every customer will be given download links inside of their account area for all payments made to their account.

Customers can access their account area by logging in and going to the page that contains the  [subscription_details] shortcode. From that page an invoice can be viewed and/or downloaded for any payment record.

Site administrators may also view invoices for member payments  from the Payments page under the Restrict Menu.