Buyers do get a notification email after a successful transaction and will see a PayPal Thank You page at the completion of the Checkout Process. Note, you cannot customize either.
If you want you display your own Thank You page, you need to enable the Auto Return feature in your PayPal Account.
Log in to your Account
Select "Edit Profile"
Under "Selling Preferences"
Select "Website Payment Preferences"
Note first option – Select "On" – Auto Return for…
Setup a free autoresponder for your site with paypal

See original post by pradeephuggy