How can I add captcha to the order form

cant see why not.
there are a bunch of action hooks, you can put a shortcode on the order page or edit the template…up to you really

just to say though:

maybe one can find a reason to add a captcha.

Generally speaking though , you wont be able to send an order (therefore spam you) anyway unless you clicked on some stuff and added it to the cart in the first place. As the cart adding is done by javascript, i can’t see too many spambots (if any) wanting to or being able to spam you that way…just saying

some naughty kids they make fake orders even over the phone sometimes. I don’t know what to do to stop them!

take cash up front…..:)