Painting is Shareware
Painting is shareware. That means you can try it out before you decide to buy it. It costs $20 to purchase a single copy of Painting, but there are volume discounts. Read the documentation that comes with Painting for more details.
How to Register (How to Pay)
It's fairly easy to pay for Painting, and there are many payment options. Painting comes with a convenient application called "Register" that makes forms that you can email, fax, or send through postal-mail. However, the quickest way is to pay is through the world wide web.
If you want to pay through the web, you can go to either the secure SSL page or the non-secure version. Using the secure version will encrypt your credit card information while it's in transit, but unfortunately not all web browsers work well with it. Note that unlike using the Register application, you can't get volume discounts (except for site licenses), and you can only pay with a credit card.
Information about Registration
Kagi handles my order processing, and they have pages explaining how to order. Click an item to learn more about its method of payment:
Postal Mail (slow)
It will probably be worth your while to read the document on Common Mistakes.
If you've got more questions, check out Kagi's Big How To page on ordering. And of course, you can always just contact me.