Apologies for the lengthy delay in my reply: The Apoc PDF Toolkit is capable of writing documents directly to a Stream without the need to serialise anything to disk. Here is an example to illustrate: PdfDocument file1 = new PdfDocument(...); PdfDocument file2 = new PdfDocument(...); // Create a collection of pages from file 2 PdfPageCollection pageCol = file2.Pages; // Add the pages from the collection to file 1 foreach (PdfPage page in pageCol) { file1.Pages.Append(page); } // Write PDF to in-memory buffer MemoryStream ms = new MemoryStream() file1.Write(ms); Response.Clear(); Response.AppendHeader("content-disposition", "filename=concat.pdf"); Response.ContentType = "application/pdf"; byte[] bytes = ms.ToArray(); Response.OutputStream.Write(bytes, 0, bytes.Length); Response.End(); If you require any further information please do not hesitate to get in touch - support@chive.com Regards Chive Software