public static void MergePdf() { using (MemoryStream stream = new MemoryStream()) { PdfDocument pdfDoc = new PdfDocument(new PdfWriter(stream)); iText.Kernel.Utils.PdfMerger merger = new iText.Kernel.Utils.PdfMerger(pdfDoc); foreach (byte[] pdf in Pdfs) { PdfDocument currentPdf = new PdfDocument(new PdfReader(new MemoryStream(pdf))); merger.Merge(currentPdf, 1, currentPdf.GetNumberOfPages()); currentPdf.Close(); } merger.Close(); pdfDoc.Close(); FinalMergedPdfURL = Format + Convert.ToBase64String(stream.ToArray()); } IsSubmitComplete = true; IsMergeComplete = true; }