Yes. Your first 30 days of Pro are free, whether you upgrade on the web, in the iOS app, or in the Android app. Then Pro is $3.99 a month.
- Each person gets one Pro trial, across the web and the app stores. If you had Pro or a Pro trial before, Pro starts paid.
- You add a card (on the web) or use your App Store or Google Play account. Cancel before the trial ends and you pay nothing; otherwise Pro renews monthly until you cancel.
- In the App Store, cancel at least 24 hours before the trial ends.