C# word生成PDF加水印

/// <summary>
        /// 生成水印PDF
        /// </summary>
        /// <param name="templatePath">水印模板</param>
        /// <param name="savePath">保存PDF的路径</param>
        /// <param name="wordPath">Copy的新word模板</param>
        /// <param name="contextPath">合同文本</param>
        public string ConvertPDF(string templatePath, string savePath, string wordPath, string contextPath)
        {
            object missing = Type.Missing;
           // ApplicationClass wordApp = null;
            Microsoft.Office.Interop.Word.Application wordApp = null;
            Document docNewWord = null;
            try
            {
                if (!IOUtility.CopyFile(contextPath, wordPath, true))
                {
                    LogUntitly.WriteLog(typeof(LhWordAddinUntitly), contextPath + "此路径文件不存在！");
                    return "";
                }
                //File.Copy(contextPath, wordPath, true);
                //wordApp = new ApplicationClass();
                wordApp = new Microsoft.Office.Interop.Word.Application();

                //操作新合同文档
                docNewWord = wordApp.Documents.Open(wordPath);
                Document docWaterMark = wordApp.Documents.Add(templatePath);

                //使用word模板添加构建基块
                Template template = (Template)docNewWord.get_AttachedTemplate();
                Range templateHeaderRange = docNewWord.Sections[1].Headers[WdHeaderFooterIndex.wdHeaderFooterPrimary].Range;
                WdParagraphAlignment headerAlignment = templateHeaderRange.ParagraphFormat.Alignment;
                Range waterHeaderRange = docWaterMark.Sections[1].Headers[WdHeaderFooterIndex.wdHeaderFooterPrimary].Range;
                BuildingBlock waterMark = template.BuildingBlockEntries.Add("newWaterMark", WdBuildingBlockTypes.wdTypeWatermarks, "General", waterHeaderRange);

                //插入已添加到模板的水印生成块
                templateHeaderRange.Collapse(WdCollapseDirection.wdCollapseEnd);
                waterMark.Insert(templateHeaderRange, true);

                //页眉格式调整
                Range rg = docNewWord.Sections[1].Headers[WdHeaderFooterIndex.wdHeaderFooterPrimary].Range;
                var rText = rg.Text.Replace("\r", "").Replace("\n", "");
                var leng = rText.Length;
                if (leng > 0)
                {
                    docNewWord.Sections[1].Borders[WdBorderType.wdBorderBottom].LineStyle = WdLineStyle.wdLineStyleNone;
                    rg.ParagraphFormat.Alignment = headerAlignment;
                    rg.Collapse(WdCollapseDirection.wdCollapseEnd);
                    rg.MoveStart(WdUnits.wdCharacter, 1);
                    rg.Delete(WdUnits.wdCharacter, 1);
                }

                docNewWord.Save();
                docNewWord.ActiveWindow.View.Type = WdViewType.wdNormalView;
                docNewWord.ActiveWindow.View.Type = WdViewType.wdPrintView;
                docNewWord.ActiveWindow.View.ShowRevisionsAndComments = false;
                docNewWord.ExportAsFixedFormat(savePath, WdExportFormat.wdExportFormatPDF);
                return "ok";
            }
            catch (Exception e)
            {
                LogUntitly.WriteLog(typeof(LhWordAddinUntitly), e);
                return "";
            }
            finally
            {
                if (docNewWord != null)
                {
                    object notsavechange = WdSaveOptions.wdDoNotSaveChanges;
                    docNewWord.Close(ref notsavechange, ref missing, ref missing);
                }
                if (wordApp != null)
                {
                    wordApp.Quit();
                    System.Runtime.InteropServices.Marshal.ReleaseComObject(wordApp);
                }
            }
        }