PDF Mosaic: How to create layers (Optional Content Groups) in PDF

using PDFMosaic;
using System;
 
namespace AddLayers
{
  class AddLayers
  {
    static void Main()
    {
      PDFDocument document = new PDFDocument();
      PDFPage page = new PDFPage(PDFPaperFormat.A4);
      document.Pages.Add(page);
      PDFCanvas canvas = page.Canvas;
 
      PDFSolidBrush br = new PDFSolidBrush(new PDFColorRGB(0, 0, 255));
 
      PDFLayer allContents = new PDFLayer("All contents");
      canvas.BeginMarkedContent(allContents);
 
      PDFLayer circle = new PDFLayer("Circle");
      canvas.BeginMarkedContent(circle);
      canvas.DrawCircle(br, 100, 100, 50);
      canvas.EndMarkedContent();
 
      PDFLayer text = new PDFLayer("Text");
      canvas.BeginMarkedContent(text);
      br.Color = new PDFColorRGB(0, 0, 0);
      canvas.DrawString("Text text", new PDFFont(PDFStandardFont.Helvetica, 14), br, 200, 100);
      canvas.EndMarkedContent();
 
      canvas.EndMarkedContent();
 
      document.OptionalContents.Layers.Add(circle);
      document.OptionalContents.Layers.Add(text);
      document.OptionalContents.Layers.Add(allContents);
 
      PDFOptionalContentGroup group = new PDFOptionalContentGroup();
      group.Add(new PDFOptionalContentGroupLayer(circle));
      group.Add(new PDFOptionalContentGroupLayer(text));
 
      document.OptionalContents.Configuration.Order.Add(new PDFOptionalContentGroupLayer(allContents));
      document.OptionalContents.Configuration.Order.Add(group);
 
      document.PageMode = PDFPageMode.OptionalContent;
      document.Save("AddLayers.pdf", true);
    }
  }
}