Add icon and text to Signature Annotation

How can I add Image like icon and text, for example the signature name, in a signature annotation on my PDF?

This is already implemented in the Xamarin demo project (setting a graphical signature using SetIcon).

To change/modify implementation, you need to modify the native java project.

For a guide check handleSignatureField in PDFLayoutView

I don't found anything like that in Xamarin Demo project. In Demo Project I have only the main activity with action for open pdf file.

Please can you share me the Demo Xamarin Project that contain this functionality?