It's nice to see you here today, @Lewis2,
You've got the right place to help you with your QuickBooks questions. I can share some insights on how to save invoices in PDF format.
There are 2 ways to do that in QuickBooks. Follow the steps below:
Option 1: In the Sales tab.
- Go to the Sales menu.
- Tap the Invoice tab.
- Mark the invoices you want to save.

- Click the Batch actions button.
- Choose Print invoices to open the PDF window.
- Click the Download icon at the top right section of the PDF screen.

Option 2: On the invoice.
- Open the invoice.
- Click on Print or Preview twice.

- On the PDF screen click the Download icon.

That should get you what you need for today. You can also check this article to learn more about emailing or printing invoices: How to email or print an invoice?
I'm just a post away if you have additional questions. You have me here to help you out. Have a good one!