if you ask for help you need to be more specific in the forum. Like , for example, what iOS version are you currently running in your problematic Apple device?
What is the latest update version of the Reader Mobile app that you have ?
Was the app working before and it crashed after any updates were applied in your device?
It is my understanding that Adobe doesn't provide direct technical support for the free Adobe Reader mobile app. Please also consult with Apple to get the appropriate technical support for this app for your iOS device.