Paypal invoice integration with Express Checkout

[yorenda]

Is there any way to integrate Paypal invoicing with express checkout? The flow we want to implement is the following:

1. Customer chooses product and buys it with paypal express checkout.
2. After the successful payment we need to send him and invoice from an invoice template with have in our business account.
3. Then we can list/filter/export our invoices to our accountant.

I tried to implement it with python SDK:

1. Create the payment from server side.
2. After payment success i created the invoice.
3. Then I updated my invoice as PAYED
4. Then i tried to send invoice to client, but Paypal API complains that i cannot send a PAYED invoice to client. 

The thing is that i don't want the invoice to have payment at all and i could not find a way to send my self updated invoice as PAID to client 

just as PDF as HTML.

[tonkol]

@yorenda did you find a solution to this? I do not understand why is this does not work without any coding actually. This is the most basic checkout flow...