Hi there, Autobadges.
The Premier version allows up to 5 users while you can only add 3 with Pro. Just make sure that they have access to Sales and Accounts Receivable section so they can see the invoices. Also, we recommend that all users should be using the same version and on the same license to avoid data damage and restriction issues.
Please see these links and guide articles for more details:
Reply to this thread if you need anything else. I'd be glad to get back here and help you again.
