PDF header signature not found - Really confused about this

private void Word2PDF()
        {
            //Create a new Microsoft Word application object
            Microsoft.Office.Interop.Word.Application word = new Microsoft.Office.Interop.Word.Application();

            //Adding dummy value because c# doesn't have optional arguments
            object oMissing = System.Reflection.Missing.Value;

            //Getting list of word files in specified directory
            DirectoryInfo dirInfo = new DirectoryInfo("C:\\TestFilestore\\");
            FileInfo[] wordFiles = dirInfo.GetFiles("*.doc");
            word.Visible = false;
            word.ScreenUpdating = false;

            foreach (FileInfo wordFile in wordFiles)
            {
                //Cast as object for word open method
                Object filename = (Object)wordFile.FullName;

                Microsoft.Office.Interop.Word.Document doc = word.Documents.Open(ref filename, ref oMissing,
                                                    ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing,
                                                    ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing,
                                                    ref oMissing, ref oMissing, ref oMissing, ref oMissing);
                doc.Activate();

                object outputFileName = wordFile.FullName.Replace(".doc", ".pdf");
                object fileFormat = WdSaveFormat.wdFormatPDF;

                //Save document into pdf format
                doc.SaveAs(ref outputFileName,
                    ref fileFormat, ref oMissing, ref oMissing,
                    ref oMissing, ref oMissing, ref oMissing, ref oMissing,
                    ref oMissing, ref oMissing, ref oMissing, ref oMissing,
                    ref oMissing, ref oMissing, ref oMissing, ref oMissing);

                //close the word document, but leave the word application open.
                //doc has to be cast to type_document so that it will find the correct close method.
                object saveChanges = WdSaveOptions.wdDoNotSaveChanges;
                ((_Document)doc).Close(ref saveChanges, ref oMissing, ref oMissing);
                doc = null;
            }

            //word has to be case to type_application so that it will find the correct quit method.
            ((_Application)word).Quit(ref oMissing, ref oMissing, ref oMissing);
            word = null;

        }

static public void CopyPages(string source, string dest)
        {
            var reader = new iTextSharp.text.pdf.PdfReader(source);
            using (FileStream fs = new FileStream(dest, FileMode.Create, FileAccess.Write, FileShare.None))
            {

                iTextSharp.text.Document doc = new iTextSharp.text.Document(reader.GetPageSizeWithRotation(1));
                {
                    //Use a PdfCopy to duplicate each page
                    iTextSharp.text.pdf.PdfCopy copy = new iTextSharp.text.pdf.PdfCopy(doc, fs);
                    {
                        doc.Open();
                        copy.SetLinearPageMode();
                        for (int i = 1; i <= reader.NumberOfPages; i++)
                        {
                            copy.AddPage(copy.GetImportedPage(reader, i));
                        }
                        //Reorder pages
                        //copy.ReorderPages(new int[] { 2, 1 });
                        doc.Close();
                    }
                }
            }
        }

var reader = new iTextSharp.text.pdf.PdfReader(source);