If you don't want people to save things to Pinterest from your website, just paste this code into the <head> section of any page on your site:
<meta name="pinterest" content="nopin" />
When someone tries to save things to Pinterest from your site, they'll see: "This site doesn't allow saving to Pinterest. Please contact the owner with any questions. Thanks for visiting!"
You can customise the message by adding a description to the meta tag:
<meta name = "pinterest" content = "nopin" description = "Sorry, you can't save from my website" />
If you want to turn off saving to Pinterest on a single image, add this tag to it:
<img src = "foo.jpg" nopin = "nopin" />