I see that sending an invoice as a PDF is more convenient on your end, Atkinson. I have some information that can clear up about the Gear icon and the Account and Settings you mentioned.
The options you stated are available in QuickBooks Online (QBO) and not in QuickBooks Self-Employed (QBSE). You might have followed instructions that do not fit to the product you utilize.
With regard to sending PDF invoices directly to your customers, this option is currently unavailable in QBSE. You can, however, create an entry and then utilize the print or export option to save it as a PDF. Then, manually email them to your clients.
If you wish to have this functionality to directly send the invoice as a PDF, I recommend upgrading your plan to QBO. You can click this link for the plans and pricing: https://quickbooks.intuit.com/au/pricing/
Once you have decided to upgrade, you can read this article to learn how to activate the option to send it as a PDF: Send an invoice to a customer.
Your convenience in sending an invoice is our utmost priority. If you need additional assistance in managing your sales entries, you can leave a reply below.