In short, yes.
Subscriptions can be used on two devices by the same user (with the same iTunes account).
If you have a subscription working on one device and are trying to setup on a second device, follow these instructions:
1) First, on your working device, sign in (or create a LawStack account) in Settings > Account.
2) Second, on your additional device, sign in the same way.
3) Visit the Subscription view on both devices and press the refresh button (icon in the upper right) to sync across devices.
And you’re done! If you have any questions, please contact us at support@lawstack.com.