Can I upgrade to a different plan at a later time?

Yes!

Head to your account > View Licenses

Choose ‘View Upgrades’

 

Choose ‘Upgrade License’

Follow steps to checkout.

 

Upgrading from Pro to LTD?

You will need to deactivate and reactive your AB Split Test License in your website admin to enable the new Agency features. Go to WP Admin > Settings > AB Split Test > Deactivate License. Then Activate License