How do I add the option to share a link to the estimate or invoice to a customer?

I can help you with this, hello140.

You'll have the option to save and share a link when creating invoices in QuickBooks Online. If you have created an estimate, you can convert it into an invoice before seeing this option. I'll show you how.

1. Go to the Sales menu.
2. Select All Sales.
3. Locate the estimate.
4. In the Action column, click Create invoice.
5. Choose Save and share a link from the dropdown list,
6. Hit the Copy link button to send your customer a link.

I've also included this article to show you how to personalize your sales transactions: Customize invoices, estimates, and sales receipts in QuickBooks Online.

If you have further questions related to estimating or invoices, please add them to your reply below. I'm always here to assist you. Have a good one.