Question 

How to enable and disable 14-day trial period in BCR for iOS and FineReader PDF for iOS applications?

Answer

If you have never subscribed to a yearly Premium account before, you will have the option of getting a free 14-day trial period. Canceling the trial period will immediately disable your subscription. Payment for subscription renewals will be charged to your account within 24 hours period to the end of the current period.

You can disable subscription renewals in your iTunes account settings on your device: How to cancel the subscription to Premium Account in an iOS application?