Using PDFsharp to Open 128-bit AES Encrypted Files

I am getting PDF files that I have processed using the PDFsharp libraries. These files are where 128-bit RC4 is encrypted. Now I am getting files that are 128-bit AES encyption.

I am getting this exception. The PDF document is protected with encryption not supported by PDFsharp.

Is AES just not supported, or do I need to change the method in which I open the file?

     Using InDoc As PdfDocument = PdfReader.Open(InputFileName, Password, PdfDocumentOpenMode.Import)
            Using OutDoc As PdfDocument = New PdfDocument
                For Each page As PdfPage In InDoc.Pages
                    OutDoc.AddPage(page)
                Next
            End Using
  End Using