internal void LoadOCGs()
{
    this.CheckedListBox1.Items.Clear();
    ViewStates.Clear();
    if (!pdfOCGs == null)
        pdfOCGs.Clear();
    pdfOCGs = new List<Patagames.Pdf.Net.BasicTypes.PdfTypeDictionary>();
    pdfRoot = PdfViewer1.Document.Root;
    // (Optional; PDF 1.5; required if a document contains optional content)
    // dictionary or array of dictionaries specifying the optional content
    // groups whose states determine the visibility of content controlled by this membership dictionary.

    // Note: Null values or references to deleted objects are ignored. If this entry is not
    // present, is an empty array, or contains references only to null or deleted objects, the
    // membership dictionary has no effect on the visibility of any content.

    // It may be a dictionary not an array. Please check it for other documents. 
    // All provided documents contains an array in that entry.
    var oc_prop = GetDictionary(pdfRoot, "OCProperties", null/* TODO Change to default(_) if this is not a reference type */, false);
    var ocgs = oc_prop("OCGs") as Patagames.Pdf.Net.BasicTypes.PdfTypeArray;
    var list = Patagames.Pdf.Net.BasicTypes.PdfIndirectList.FromPdfDocument(PdfViewer1.Document);
    foreach (object Item in ocgs)
    {
        var ocg = Item as Patagames.Pdf.Net.BasicTypes.PdfTypeIndirect.Direct as Patagames.Pdf.Net.BasicTypes.PdfTypeDictionary;
        // A usage dictionary describing the nature of the content controlled by
        // the group. It may be used by features that automatically control the state of the
        // group based on outside factors. See “Usage and Usage Application Dictionaries”
        // on page 380 for more information.
        var usage = GetDictionary(ocg, "Usage", list);
        // A dictionary that has a single entry, ViewState, a name that may have a
        // value of ON or OFF, indicating that the group should be set to that state when the
        // document is opened in a viewer application.
        var view = GetDictionary(usage, "view");
        Patagames.Pdf.Net.BasicTypes.PdfTypeName viewState = null/* TODO Change to default(_) if this is not a reference type */;
        if (!view.ContainsKey("viewState"))
        {
            viewState = Patagames.Pdf.Net.BasicTypes.PdfTypeName.Create("OFF");
            view.Add("viewState", viewState);
        }
        else
        {
            var t = view("viewState");
            var V = (Patagames.Pdf.Net.BasicTypes.PdfTypeName)t;
            viewState = view("viewState") as Patagames.Pdf.Net.BasicTypes.PdfTypeName;
        }
        var Name = ocg.GetStringBy("Name");
        var ni = CheckedListBox1.Items.Add(Name, viewState.Value.ToString == "OFF" ? false : true);
        ViewStates.Add(viewState);
        pdfOCGs.Add(ocg);
    }
}

private void CheckedListBox1_ItemCheck(object sender, System.Windows.Forms.ItemCheckEventArgs e)
{
    var Test = e.CurrentValue;
    var Index = e.Index;
    var ViewState = ViewStates(Index);
    ViewStates(Index).Value = Test == CheckState.Checked ? "ON" : "OFF";
    PdfViewer1.CurrentPage.Dispose();
    PdfViewer1.ClearRenderBuffer();
    PdfViewer1.Invalidate();
}

public PdfTypeDictionary GetDictionary(PdfTypeDictionary parent, string entry, PdfIndirectList list = null, bool is_create = true)
{
    PdfTypeDictionary ret = null;
    if (!parent.ContainsKey(entry))
    {
        if(!is_create)
            throw new Exception(string.Format("The document does not have {0} entry", entry));

        ret = PdfTypeDictionary.Create();
        if (list != null)
        {
            list.Add(ret);
            parent.SetIndirectAt(entry, list, ret);
        }
        else
            parent.SetAt(entry, ret);
    }
    else if (parent[entry] is PdfTypeIndirect)
        ret = (parent[entry] as PdfTypeIndirect).Direct as PdfTypeDictionary;
    else if (parent[entry] is PdfTypeDictionary)
        ret = parent[entry] as PdfTypeDictionary;
    else
        throw new Exception(string.Format("'{0}' entry has unknown type", entry));

    return ret;
}

public Form1()
{
    InitializeComponent();
    PdfCommon.Initialize();

    pdfViewer1.LoadDocument(@"d:\10\axf-layer-1.pdf");
    //pdfViewer1.LoadDocument(@"d:\10\House_Plan_Final.pdf");
    //pdfViewer1.LoadDocument(@"d:\10\Layers.pdf");

    //The catalog dictionary for the PDF document contained in the file
    var root = pdfViewer1.Document.Root;

    //The document’s optional content properties dictionary (see Section 4.10.3,
    //“Configuring Optional Content”).
    //(Optional; PDF 1.5; required if a document contains optional content)
    var oc_prop = GetDictionary(root, "OCProperties", null, false);

    //dictionary or array of dictionaries specifying the optional content
    //groups whose states determine the visibility of content controlled by this membership dictionary.
    //Note: Null values or references to deleted objects are ignored. If this entry is not
    //present, is an empty array, or contains references only to null or deleted objects, the
    //membership dictionary has no effect on the visibility of any content.

    //It may be a dictionary not an array. Please check it for other documents. 
    //All provided documents contains an array in that entry.
    var ocgs = oc_prop["OCGs"] as PdfTypeArray;

    var list = PdfIndirectList.FromPdfDocument(pdfViewer1.Document);
    foreach (var item in ocgs)
    {
        var ocg = (item as PdfTypeIndirect).Direct as PdfTypeDictionary;

        //A usage dictionary describing the nature of the content controlled by
        //the group. It may be used by features that automatically control the state of the
        //group based on outside factors. See “Usage and Usage Application Dictionaries”
        //on page 380 for more information.
        var usage = GetDictionary(ocg, "Usage", list);

        //A dictionary that has a single entry, ViewState, a name that may have a
        //value of ON or OFF, indicating that the group should be set to that state when the
        //document is opened in a viewer application.
        var view = GetDictionary(usage, "View");

        PdfTypeName viewState = null;
        if (!view.ContainsKey("ViewState"))
        {
            viewState = PdfTypeName.Create("OFF");
            view.Add("ViewState", viewState);
        }
        else
            viewState = view["ViewState"] as PdfTypeName;

        viewState.Value = "OFF";
    }
    pdfViewer1.ClearRenderBuffer();
    pdfViewer1.Invalidate();
}