1. When you Create a new or Edit an existing invoice, you can send it via email to your Partner
2. Click the Save and Send button
3. Modify the Subject and the email body if you want.
4. Attach a PDF if you want
5. Accept PayPal payment if you want, so can get paid faster
6. Decide you want to receive a copy of the same e-mail that your Partner will receive.
7. Click send and you are done
And this is an example of what your Partner will receive.