Yes, you can attach a tracker when you pin to Pinterest. Here's how I do it:
Log onto Pinterest and click on Add a Pin. Copy the URL of the targeted hub that includes your tracker number into the URL box. This will bring up a screen where you can select a picture in the hub. Do that and select the category. Save the pin.
Another way to do it if you have Pinterest on your tool bar is to pin it, then click on "See my Pin". When you get to the next screen, you can click on EDIT and it will bring up the URL of your pin. At this point, you can add your tracker to the URL. You can also change the category if you accidentally put it into a wrong group. Be sue to click Save Pin.
I don't use the Pin button within the hub because it's even more roundabout to get to the edit screen where you can add your tracker.