Stream outputStream = new FileStream("path", FileMode.OpenOrCreate, FileAccess.ReadWrite)

        private void radButton1_Click(object sender, EventArgs e)
        {
            this.radPdfViewer1.ShowThumbnails();
        }

        private void radButton2_Click(object sender, EventArgs e)
        {
            this.radPdfViewer1.ShowBookmarks();
        }

        public TestRadForm()
        {
            InitializeComponent();
            this.radPdfViewer1.LoadDocument(@"..\..\..\SampleDocument.pdf");
        }

        private void radButton1_Click(object sender, EventArgs e)
        {
            this.radPdfViewer1.Document.AcroForm.FlattenFormFields();
            this.radPdfViewer1.SaveDocument(@"..\..\saved.pdf");
        }

        static void Main(string[] args)
        {
            int i = 1;
            try
            {
                Stopwatch stopwatch = Stopwatch.StartNew();
                while (true)
                {
                    using (RadPdfViewer pdfViewer = new RadPdfViewer())
                    {

                    }
                    Console.WriteLine($"iteration {i}, elapsed seconds: {stopwatch.Elapsed.TotalSeconds}");
                    i++;
                }
            }
            catch (Exception e)
            {
                Console.WriteLine($"Exception occurred at iteration {i}");
                Console.WriteLine(e);
                Console.ReadLine();
            }
        }

System.Runtime.InteropServices.ExternalException (0x80004005): A generic error occurred in GDI+.
   at System.Drawing.Bitmap.GetHicon()
   at Telerik.WinControls.PdfViewer.MouseHandlers.PanHandler..ctor(MouseHandlersController controller, IFixedDocumentPresenter presenter)
   at Telerik.WinControls.PdfViewer.MouseHandlers.MouseHandlersController.BuildHandlers(IFixedDocumentPresenter presenter)
   at Telerik.WinControls.PdfViewer.MouseHandlers.MouseHandlersController..ctor(IFixedDocumentPresenter presenter)
   at Telerik.WinControls.UI.RadPdfViewerElement..ctor()
   at Telerik.WinControls.UI.RadPdfViewer.CreateViewerElement()
   at Telerik.WinControls.UI.RadPdfViewer.CreateChildItems(RadElement parent)
   at Telerik.WinControls.RadControl.Telerik.WinControls.IComponentTreeHandler.CreateChildItems(RadElement parent)
   at Telerik.WinControls.RadElementTree.InitializeRootElement()
   at Telerik.WinControls.RadControl.Construct()
   at Telerik.WinControls.RadControl..ctor()
   at Telerik.WinControls.UI.RadPdfViewer..ctor()