You’ll be able to change your subscription plan from Printful Pro to Plus at any given time, but to start enjoying your Printful Plus plan, you’ll first need to wait until the current billing period for Pro ends.
To change your subscription, go to your Dashboard > Settings > My account > Subscription plan. Once you’re there, choose to cancel your Pro subscription and you’ll be asked if you’d rather switch your subscription to the Printful Plus plan. Click the button Switch to Printful Plus to change your plan to Plus.
If you wish to change your monthly plan to a yearly one (or vice versa), then cancel your existing subscription and resubscribe to your chosen plan.