Give Them The PDF They Want: For some clients, the imbedded receipt/receipt in the Shopify request affirmation email isn't adequate. They need a downloadable file.
Save Time For Everyone: By placing a connection in each request affirmation, you're letting clients self-serve the PDF they need. No messages/calls necessary.
You're A Responsive Company: Have your clients been requesting this element for some time? Give them you're tuning in.