Hey Alex, sorry for the confusion! It's a semi manual process currently for Every subscribers, all you need to do is click the Upgrade button and it should turn on Pro by linking ti your Every account if you've used the same email address for both. You shouldn't need to go through the payment flow, so ping me if you don't see that.

There is an iPhone app in beta (being actively worked on right now ready for full release), once you're set up as pro you can find the link in the user menu on any doc as shown below.

Let me know if you have any other q's!