It has a number of tools, pencil, highlighter, underline, note, and stamp tools.
It stores and accesses your files from the cloud including Google Drive, Microsoft OneDrive, and Box.
Yous can annotate PDF files, draw and highlight PDF text easily.
And finally, their cloud sync service allows you to stay connected to your files wherever you go. iAnnotate PDF is optimized for tablets but it works pretty well on smartphones. There is a Getting Started page and Quick Reference Guide that helps new users to get to know the strength of the program in minimal time. It consists of the typical annotation tools such as Pen, Highlighter, Underline. iAnnotate PDF's interface gives you the desktop PC feel while at the same time allowing you to use android's touch screen functionality. It makes a perfect balance between providing sufficient tools yet not sacrificing on the UI. iAnnotate PDF is one of the best apps for annotating PDF files. Yet, the best thing about the Android version is that it is free as compared to the paid iPad version. Its popularity in iPad devices pushed it to be started on Android devices. IAnnotate PDF was originally released for Apple's iPad.