Is there a way to automatically attach the PDF file of an invoice when sending an email?

Great to have you here in the Community, james-jebcoconst.

Invoices in QuickBooks Online (QBO) should normally attach PDF files as long as this feature is turned on. With this, let's go ahead and check if it was enabled. Here's how:

1. Go to the Gear icon and select Account and Settings.
2. Choose the Sales tab and click Online delivery.
3. Check the PDF Attached box and Save.

Additionally, if you want to add files/images to your desired invoice you can follow this guide: Add or delete attachments in QuickBooks Online.

Furthermore, you can also check out this article on how to get transactions from your bank and import them into QBO: Manually upload transactions into QuickBooks Online.

Don't hesitate to click reply if you have any other invoice or QuickBooks-related concerns. Have a great day ahead.