Question 

How to change the subscription type, for instance, how to convert the monthly/yearly subscription for IOS into lifetime or monthly subscription to yearly

Answer

There is no mechanism to change the subscription type for iOS (BCR, FineReader PDF for Mobile). We can only recommend you the following solution:

1. Please cancel the current subscription (How to cancel the subscription to Premium Account in iOS application?).

2. Ask Apple for the refund (How can I refund purchased iOS application?). 

3. Purchase the new subscription which you need.

You may also wait until the subscription ends, cancel it and then purchase the new one.