Can I link another email account to my current/paid account?

Yes, you can add additional users to your plan directly from the pricing page. Once you have purchased additional seats for your workspace, here is how you can invite/add users. 

Here are the team size limits for each plan:

• Basic: 1 - 10 users
• Pro: 1- 10 users
• Enterprise: 5 -  25+ users

Here is how ading and removing users affects your billing.