Isn't a voucher or coupon a digital download? Yes it is.
But when it comes to vouchers for printing on canvas, photo books, calendars, etc., we do often charge shipping when you purchase with us.
We're not trying to pull a quick one: this is to make sure you don't have to pay when your prints are sent to you by the printing business themselves.
In other words, it's not shipping to get your voucher to you, but rather a pre-payment of the shipping charge to get your printed product to you.
We haven't always done it this way, but we find that if we don't charge shipping, our customers end up with an unpleasant surprise when they process their prints and find out only then that there's more to be paid.