Hi,
Normally, after the status of an order changes from "created" to "confirmed", an email of the type "order status notification" is sent and it should appear in the Customers>Emails history menu.
And normally, that email should contain the PDF invoice of the plugin if activated.
If you don't have that order status notification in the email history, check that the email is enabled in the System>Emails menu.
If it is, then it could be linked to the payment method you're using which changes the status of the order to confirmed.
Which payment method are you using ?