PDFsharp & MigraDoc Foundation

        public void MssTwoLanePDF(byte[] ssinputPDF, out byte[] ssoutputPDF) {
         ssoutputPDF = new byte[] {};
            MemoryStream stream = new MemoryStream(ssinputPDF);

            // Create the output document
            PdfDocument outputDocument = new PdfDocument();

            // Show single pages
            // (Note: one page contains two pages from the source document)
            outputDocument.PageLayout = PdfPageLayout.SinglePage;
            XGraphics gfx;
            XRect box;

            // Open the input document stream as XPdfForm object
            XPdfForm form = XPdfForm.FromStream(stream);
            double width = form.PixelWidth;
            double height = form.PixelHeight;


            // Add a new page to the output document
            PdfPage page = outputDocument.AddPage();
            page.Width = new XUnit(width * 2);
            page.Height = new XUnit(height);

            gfx = XGraphics.FromPdfPage(page);

            // Draw first lane
            //box = new XRect(0, 0, width, height);
            //gfx.DrawImage(form, box);
            gfx.DrawImage(form, 0, 0, width, height);

            // Draw second lane
            box = new XRect(width, 0, width, height);
            //gfx.DrawImage(form, box);
            gfx.DrawImage(form, width, 0, width, height);

            // Save the document...
            MemoryStream outputstream = new MemoryStream();
            //Save the document into stream
            outputDocument.Save(outputstream);

            //Save the stream as a file in the ssoutputPDF variable
            ssoutputPDF = outputstream.ToArray();