The most important of these is the rollout of two-factor authentication to all users. You can receive codes via text message or through an authentication app such as Authy. You can enable 2FA through the Security page on Account Settings after it's available to you.
Pinterest is also upgrading the Security section by listing all the devices currently logged into your account. If you see a device you don't recognize, you can remove it from this page. Finally, the service is also emailing users when they log in from a new device.
It's surprising it's taken Pinterest so long to enable such basic security options, but it's also questionable how useful they'll be. These days, most people use just a few logins -- such as Google or Facebook -- to set up accounts on multiple sites. Still, it's nice to see that more social networks are taking online security seriously.