You can upgrade to Newton Pro in the desktop app, on the web, or in the iPhone, iPad and Android apps. If you've never had Pro, it starts with a free trial.
Steps
Desktop
Open Settings: press ⌘, on Mac, or Ctrl+, on Windows and Linux.
Go to the Profile tab.
Next to Plan, click Subscribe to Pro.
Click Monthly or Yearly. Checkout opens in your browser.
Enter your card details and confirm, then click Return to Newton.
Click Monthly or Yearly, then enter your card details and confirm.
iPhone & iPad
Open the menu and tap the Settings gear at the bottom.
On the Newton Pro card at the top, tap Upgrade to Pro.
Tap the Yearly or Monthly plan, then confirm with Apple.
Android
Open the menu and tap the Settings gear at the bottom.
Tap the Newton Pro card at the top.
Under Billing, choose Monthly or Yearly.
Tap Subscribe, then confirm with Google Play.
When it's done, your plan shows Pro with the date your trial ends or your plan renews.
Good to know
On the web and in the desktop app, checkout asks for a card even for the free trial. If you don't cancel before the trial ends, your subscription starts.
You can have one free trial per Newton account on the web. In the App Store and Google Play, Apple and Google decide whether you can have a trial.
In the phone apps, you can also tap Get Newton Pro at the bottom of the menu, or the upgrade button in Recap.
App Store and Google Play prices are set for each country, so they can differ from the web price.