Add bookmarks to a PDF using Foxit ActiveX SDK pro (VBA)

Does anybody have experience with Foxit ActiveX SDK pro in Excel VBA?

I would like to add bookmarks to specific pages in a PDF using Foxit ActiveX SDK pro in Excel VBA.

Can somebody please help?

The code I have for now is this, but the last part does not work:

Sub Test_Foxit_Open_PDF_in_Userform() 

    'This will open a PDF in a userform (in excel), insert another existing PDF,
    'add a watermark and save as another PDF
    'Dim PDFPrinter As New FoxitPDFSDKProLib.FoxitPDFSDK 

    Dim sPDFfile As String, sPDFfile2 As String 

    Dim sSaveAsFileName As String 

    Dim IsFileOpen As Boolean 

    Dim lPageCount As Long 

    Dim bResult As Boolean 

    sPDFfile = "C:\Users\frank.van.eygen\Documents\PDF files\Exact3.pdf" 

    sPDFfile2 = "C:\Users\frank.van.eygen\Documents\PDF files\Test Frank.pdf" 

    sSaveAsFileName = "C:\Users\frank.van.eygen\Documents\PDF files\Test_Foxit.pdf" 

    Load UserForm1 

    IsFileOpen = UserForm1.FoxitPDFSDK1.OpenFile(sPDFfile, "") 

    lPageCount = UserForm1.FoxitPDFSDK1.PageCount 

    bResult = UserForm1.FoxitPDFSDK1.InsertPage(lPageCount, sPDFfile2, "", "0") 

    bResult = UserForm1.FoxitPDFSDK1.AddWaterMark(1, "This is a watermark", 50, 200, 90, ColorConstants.vbCyan, 0, 100, 45) 

    UserForm1.FoxitPDFSDK1.SaveAs (sSaveAsFileName) 

'adding a bookmark does not work
    'UserForm1.FoxitPDFSDK1.SetBookmarkContextMenuString ("Page1") 

    'UserForm1.FoxitPDFSDK1.GetOutlineFirstChild() 

    UserForm1.Show 

    Unload UserForm1 

End Sub