As a member pointed out yesterday, you can create gift certificates through PayPal. However, the tutorial that he kindly linked to was specifically for users of the Big Cartel e-store software. Here are some more general instructions.

Find the form to create a Gift Certificate button, for your readers to buy and give gift certificates to your store, under “Merchant Services.” It will be listed under “Create Buttons.”
The content you are trying to access is only available to members.