How do I change what my customers see on my estimates and invoices?

Two places. Settings, Workspace (/settings) holds your workspace name, logo, accent colour, website, phone, email and address, which is what a customer sees on the estimate or invoice they open. Settings, Workspace, Estimates and Settings, Workspace, Invoices hold the message that goes with the document when you send it.

On the document itself. The logo and workspace name sit at the top of the estimate and the invoice. The accent colour is used on the page a customer opens from the link you send. The PDF is deliberately black and white apart from the logo, so it stays readable printed or forwarded.

The disclaimer printed at the bottom of every estimate PDF is on Settings, Workspace, Estimates (/settings/workspace/estimates). A location can replace it with its own, which is useful when different regions need different wording: how locations change your estimate defaults.

The email that carries it. The Estimates page sets the default subject and body of the estimate email, and the schedule for reminders when a customer has not responded. The Invoices page (/settings/workspace/invoices) does the same for invoices, plus the payment receipt email and whether receipts are sent at all. Invoice reminders are off by default and begin the day after an invoice's due date when you turn them on. Both pages give you the default we ship, so you can edit it rather than start from a blank box.

The numbers on the document come from your defaults rather than from this page: tax rate and profit margin in how to set your default tax rate, overhead and margin, and the validity window in how to change how long estimates stay valid.

All of this needs the "Manage workspace settings" permission, and it changes what every future document looks like, not the ones already sent.