using(var inputDocument = PdfReader.Open(@"C:\temp\PdfTemplates\MyPdf.pdf"))
{
   PdfDictionary outline = (PdfDictionary)inputDocument.Internals.Catalog.Elements.GetObject("/Outlines");
   PdfDictionary first = (PdfDictionary)outline.Elements.GetObject("/First");
   PdfDictionary last = (PdfDictionary)outline.Elements.GetObject("/Last");
   var iterator = first;
   var dict = new Dictionary<string, PdfPage>();
   do
   {
      PdfReference next = iterator.Elements.GetReference("/Next");
      if (next != null)
      {
         PdfOutline nextOutline = new PdfOutline(next.Value as PdfDictionary);
         dict.Add(nextOutline.Elements.GetString("/Title"), nextOutline.DestinationPage); // DestinationPage here is null
         iterator = nextOutline;
         break;
      }
   }
   while (PdfInternals.GetObjectID(iterator) != PdfInternals.GetObjectID(last));