The following are utility classes that can be used in Xamarin PDF viewer for annotation creation, editing, etc.

Xamarin.Android C#

• pdftron.PDF.Tools.ToolManager
  A class containing methods for interacting with tools.

• pdftron.PDF.Annot
  A base class for different types of annotations. Specific properties should refer to derived classes.

Xamarin.iOS C#

• pdftron.PDF.Tools.PTToolManager
  A class responsbile for forwarding events from the PDFViewCtrl to Tools, and coordinating the control and data flow between tools.

• pdftron.PDF.Annot
  A base class for different types of annotations. Specific properties should refer to derived classes.