If you wish change the number of seats (number of machines using the license), you are required to login to your PassMark Account. If you have not set up your PassMark Account please use the "Forgot password?" link with your purchase e-mail address to create your account.
Once you have logged on, navigate to 'My Subscriptions' from the menu on the left. This should present your subscription plan as in the image below. From here, click 'Edit'.
This will allow you to change the number of seats for your plan and edit your payment method if needed.
If you increase the number of seats, you will be charged on a pro rata basis for the difference from your existing plan. Reducing the number of seats will be pro rata credited to your next bill.
You can cancel your subscription any time via your PassMark Account. Upon cancellation, your latest payment is non-refundable and your service will continue until the end of that month’s billing period.