Public Enum to define annotation state model.

// Load an existing PDF document
let document: PdfDocument = new PdfDocument(data, password);
// Access first page
let page: PdfPage = document.getPage(0);
// Access the annotation at index 0
let annotation: PdfPopupAnnotation = page.annotations.at(0) PdfPopupAnnotation;
// Sets the state model of the popup annotation as marked
annotation.stateModel = PdfAnnotationStateModel.marked;
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();