How to add custom option in pdftron AdvancedViewer's Three dots menu or Kebab Menu
The overflow menu can be customized using the custom toolbar configuration
https://www.pdftron.com/documentation/xamarin/guides/getting-started/using-fragment/#customize-the-options-toolbar
https://www.pdftron.com/api/xamarinandroid/tools/api/pdftron.PDF.Config.ViewerBuilder2.html#usingcustomtoolbar