If you don't want people to Pin from your website, just copy the code below and paste it into the <head> section of any page on your site.
<meta name="pinterest" content="nopin" />
When a user tries to Pin from your site, they'll see this message:
This site doesn't allow pinning to Pinterest. Please contact the owner with any questions. Thanks for visiting!
You can customize the message to users by adding a description to the meta tag:
<meta name = "pinterest" content = "nopin" description = "Sorry, this user does not allow pinning" />
You can also disallow Pinning on a single image:
<img src = "foo.jpg" nopin = "nopin" />