A mere 3 lines of code on your website will send a clear message.
The method described in Educate Pinners with .htaccess gives results like the one your see illustrated above in the screenshot. Pinners pin the image of their choice, but only if they look back at their pinboard will they notice the copyright-warning image that has been automatically substituted. If they notice the message, typically, they will erase it themselves - saving YOU the trouble of DMCA notices, and controlling the message that pinners receive when they infringe on your copyright.
All of this magic is accomplished with just 3 lines of code in your website's .htaccess file.
That was the good news. Now, for the bad news.
A surprisingly large contingent of pinners is so stubbornly imbued with its self-given right to grab an artist's content in order to gain some measure of approval from total strangers on the internet ("followers") that after Pinterest itself has blocked them from pinning content from one's domain and receiving a pop up message that pinning isn't allowed, they press on and pin anyway, in which case they end up pinning a substituted copyright-warning image instead of the image they wished to pin.
Now, you'd think that after receiving two manners of copyright warnings, the pinner would pause, and infringe copyrights on another hapless website that isn't yours. If you were to think this, you'd be very wrong.
For after these two copyright warnings, a shocking number of pinners simply double-back with their browser back-button to the image search engine result page where they originally saw your image, and pin from there.
Because you put it on the internet, and no matter how many times they're warned not to take it, they're going to bloody grab that image to impress strangers, and enrich Ben Silbermann.
It's going to be very, very difficult to change things. Pinterest will have to yield. But the copyright-infringement platform is just that, and doesn't show signs of wanting to go legit.