Hope you are doing well. Sorry for your experience with the Acrobat Reader subscription.
Since purchasing a subscription on Android has the store manager as Google Play Store or Samsung Store, while for iOS, it becomes AppStore, there is no direct way to transfer the subscription from one portal to another.
However, what can work here is you can cancel the subscription from Google Play Store and purchase a new subscription from AppStore.
Also, if you are willing to do so, please share your details about the Android subscription with me over private messages so I can check from my end and assist you better with the details.
[To share a private message, click on my profile-> click the blue button that says send a message on the next window]