Thanks for posting to the Community, @kross1.
I can see that you have already checked the Online delivery option to send invoices. Allow me to share additional insights to accomplish sending PDF attachments to your customer's invoice.
You'll have to tick the Show full details in the email option from the Online delivery section from the Accounts and Settings. In this way, all the information in your sales entry will show up on your customer's email.
To do that:
- Click on the Gear icon at the top.
- Press on Accounts and Settings.
- Refer to the Sales section.
- Pick on the pencil icon beside Online delivery.
- Tick the Show full details in email radio button.
- Make sure to put a checkmark on the PDF Attached box.

- Select Online invoice for Additional email option for invoices.
- Hit on Save.
Once done, you'll want to open the invoices you want to send to your customer.
For more details about the different file types that you can attach to any transactions in QuickBooks, together with things you need to know when emailing them, please see this link: What transactions can keep attachments?
Feel free to visit again if you still need more help with sending your sales forms. I'll be around to assist you more. Take care always.