We're working on the ability to automatically send package purchase receipts to your client through DesignFiles.
In the meantime, you can send a receipt from Stripe (the Payment Processor). Here are the steps to do it:
1. Login to your Stripe account or use this link to go to the login page: http://stripe.com/login
2. Select Payments on the left.
3. Select the specific payment you wish to send the receipt for.
4. Scroll down and select the Send Receipt button.
5. In the Send receipt window's Send receipt to field, enter your clients' email addresses and click Send. You can enter multiple email addresses separated by commas after each email address.
6. After sending the receipt, your clients will receive the invoice by email (as seen below).