Welcome to the PayPal Community and thank you for your post!
I do understand your concern with this. When a customer makes a transaction using PayPal, an email is automatically sent to them with the payment details. This would be the receipt issued by PayPal. Please advise your customers to check their email inbox's to locate their email receipts from PayPal. This is an automated process.
You can also have a function on your website to issue receipts to your customers email address. This is something you would need to set up with your website developer.
If you have any further concerns, please don't hesitate to contact our Customer Support.
I hope this helps!