This exception seems to be related to AES algorithm PaddingMode property. 

Add a navigation pane to view attachments under a pdf. it is possible to have various attachments under a pdf file, such has another pdf. For example, when converting an email with attachments, the resulting pdf has attachments. 

RadPdfViewer has no possibility to view those right now. Could be an event and let the calling program manage this.

For our needs, I would like an event, because our attached files are also pdfs, so I could open them in a new tab

Currently, Tab selects the next control.

Attached is sample PDF document. 

Overprinting is option in the GraphicState that allows combining colors when drawing one object above another object.  It is briefly described on page 284 and page 565 in PdfReference 1.7. However, the result of overprinting is device dependent and there are no strict instructions how the result should look like. This feature also includes support for the different blending modes.

To reproduce: please run the attached sample project. If you reload the document, the horizontal scrollbar is not shown.

Workaround:
        public RadForm1()
        {
            InitializeComponent();

            this.radPdfViewer1.FitToWidth = false;
            this.radPdfViewer1.ViewerMode = Telerik.WinControls.UI.FixedDocumentViewerMode.None;
            this.radPdfViewer1.EnableThumbnails = false; 
            this.radPdfViewer1.DocumentLoaded += radPdfViewer1_DocumentLoaded;
            this.radPdfViewer1.LoadDocument(@"..\..\Go Air - Himanshe Ajeet Dubey - 17-01-2018 - Ranchi to Mumbai.pdf");
            Application.DoEvents();
        }

        private void radPdfViewer1_DocumentLoaded(object sender, EventArgs e)
        {
            Application.DoEvents();
            this.radPdfViewer1.FitToWidth = true;
        }

This functionality should be similar to the one provided by Adobe.

This is not quite a valid PDF file scenario according to PDF file specification. However, we may try handling it in order to show the correct number of pages. When the kid is of type Pages, it should be added to the pages traversal recursion only the first time it is met.

The observed issue is demonstrated in the attached image. 

Tint transformation function is used to transform Device N color in Alternate colorspace. 

RadPdfViewer can not display annotated PDF file
 Kindly,i used VintaSoft SDk to Annotate PDF File, File is annotated successfully and i can open it with Adobe Reader and see annotations is added to it
 but while i try to view annotated PDF file using RadPDFViewer File will displayed without annotations ,only original content displayed.
Kindly find my attached AnnotatedPDFfile To be loaded in RadPDfViewer

RadPdfViewer can not display annotated PDF file
 Kindly,i used VintaSoft SDk to Annotate PDF File, File is annotated successfully and i can open it with Adobe Reader and see annotations is added to it
 but while i try to view annotated PDF file using RadPDFViewer File will displayed without annotations ,only original content displayed.
Kindly find my attached AnnotatedPDFfile To be loaded in RadPDfViewer

Workaround: 

public Form1()
{
    InitializeComponent();

    string pdfFilePath = Path.Combine(Application.StartupPath, "testfile1.pdf");
    radPdfViewer1.LoadDocument(pdfFilePath);

    this.radPdfViewer1.PdfViewerElement.VScrollBar.ValueChanged+=VScrollBar_ValueChanged;
}

private void VScrollBar_ValueChanged(object sender, EventArgs e)
{
    this.radPdfViewer1.PdfViewerElement.InvalidatePages();
}