public void NewPdf(string[] Pdf)
{

    byte[] newPdf;
    MemoryStream ms = new MemoryStream();
    foreach (var onepdf in Pdf)
    {
        newPdf = System.IO.File.ReadAllBytes(onepdf);
      //newPdf=System.Convert.FromBase64String(onepdf);
      // int resultPdf = newPdf.Length;
      // ms.Write(newPdf, 0, newPdf.Length);
      // var ms = new MemoryStream(new byte[resultPdf], 0, resultPdf, true, true);
       ms.Write(newPdf, 0, newPdf.Length);
       //ms.Write(baadF00d, 0, baadF00d.Length);

       //System.Buffer.BlockCopy(newPdf, 0, resultPdf, 0, newPdf.Length);
    }
    byte[] merged = ms.GetBuffer();
   // File.WriteAllBytes("testpdf.pdf", merged);
    PdfReader reader = new PdfReader(merged);
    int n = reader.NumberOfPages;
    Document document = new Document(reader.GetPageSizeWithRotation(1));
    PdfWriter writer = PdfWriter.GetInstance(document, new FileStream("thugs.pdf", FileMode.Create));
    document.Open();
    PdfContentByte cb = writer.DirectContent;
    PdfImportedPage page;
    int rotation;
    int i = 0;
    while (i < n)
    {
        i++;
        document.SetPageSize(reader.GetPageSizeWithRotation(i));
        document.NewPage();
        page = writer.GetImportedPage(reader, i);
        rotation = reader.GetPageRotation(i);
        if (rotation == 90 || rotation == 270)
        {
            cb.AddTemplate(page, 0, -1f, 1f, 0, 0, reader.GetPageSizeWithRotation(i).Height);
        }
        else
        {
            cb.AddTemplate(page, 1f, 0, 0, 1f, 0, 0);

        }
    }
    reader = new PdfReader(merged);
    // we retrieve the total number of pages
    n = reader.NumberOfPages;
    document.Close();

}

return File(bytes, mimeType);