Yes, you are able to add licenses to your existing account and activation code.
In order to do so, be sure to purchase the new licenses with the same email address or account that you used for the original purchase. Our system will automatically place the new licenses under the same account as the original purchase.
Every purchase does automatically receive a new activation code, but our system will be able to recognize that the new licenses are under the same account as the first purchase, and it will accept the original activation code for any Mac or PC license found under that account.
If you are required to order with a purchase order, please find instructions on how to do so in our knowledge base.