I subscribed to pdf editor free trail but can't find where to cancel it

Hi I have just subscribed to an apple App Store app called "pdf editor " it's free for three days but want cancel this app as it's not what I want. It's down loaded onto my iPhone the icon is on my screen and is working but I can't find anywhere to cancel it - I have looked under subscriptions and hidden subscriptions and can't see it any where - where else can I find it to cancel