Thanks for joining in, @userinfo115. I've got you the steps to send an invoice as a PDF in QuickBooks Online. This way, it won't display the Total Amount Due from the content.

Here's how: 

1. Go to the Gear icon, then select Account Settings. 
2. Go to the Sales tab, then select Online Delivery.
3. Under "Email options for all sales forms" select "Show short summary in email."
4.  Select "Attach as pdf."
5. Under "Additional email options for invoices", select the "HTML" format

The email only contains and explains to your customers in the header that the invoice is attached as a .pdf file. 

I'm excited to share with you this article that will help you and your customers can pay their invoice online. Read through this topic: Connect your QuickBooks Payments account to QuickBooks Online.

I'm happy to know that this resolves your email invoice concerns. Take care!