Text box function in the app??

Hi -- I just downloaded the app. Where it's the text box function? I need to add a text box -- not simply text -- to the PDF. Yet I can't find that function. Why? As a consumer I can't tell you ou how frustrating it is to download an app and learn that some features are not excluded. It makes no sense in this day and age when increasingly consumers are using iPhones and iPads to do work!