I've used Clickbank for years because it saves me having a merchant account with monthly fees. The fees they charge are relatively high, but it dispenses with a lot of hassle.
When someone orders, Clickbank sends me a message and I have an autoresponder set up using Mailloop 5 that replies to the message by sending purchasers an email with attached ebook. That way I have control over who receives the ebook. To download it you need some kind of password system ... too advanced for me at present.
As I'm based in Australia, sales made through Clickbank are considered exports, so I don't have to pay Goods and Services Tax as I do when they are sold within Australia.
Before you rush off to pay Canadian and other tax, look into their requirements. You may not need to pay tax for sales through Clickbank ... depending on where you are of course.
Good luck with your new venture.
Desert Wave Enterprises