Autopost from Drupal to Pinterest?
You could set something like this up, by using Rules+Mime Mail+IFTTT.  


Set up a recipe in IFTTT that


Gets triggered when it receives an email by a specific address  
Posts on Pinterest as a reaction, using the attachment in the email  
https://ifttt.com/channels/email/triggers/50-send-ifttt-an-email-tagged

Configure Rules to send an email on an appropriate event, e.g. node updated/created


You need to use the Mime Mail to get the option to add attachments to your outgoing email
Check out this video for further information: Learn Drupal - Send email with attachments via Rules
You may need to configure your Drupal instance to use SMTP authentication on yor outgoing server to make it work with IFTTT. The PHPMailer module will probably help you with this.



Hope this helps, good luck!