int tableRow = 6 ;
   int tableColumn = 6;
    //定义一个Word中的表格对象
   Microsoft.Office.Interop.Word.Table table = document.Tables.Add(document.Paragraphs[i].Range,
   tableRow, tableColumn, ref Nothing, ref Nothing); 

 　　//默认创建的表格没有边框，这里修改其属性，使得创建的表格带有边框 
   table.Borders.Enable = 1;
   table.Cell(1, 1).Merge(table.Cell(2, 1));//纵向合并
   table.Cell(1, 1).Range.Text = "牌号/代码";

   table.Cell(1, 2).Merge(table.Cell(2, 2));//纵向合并
   table.Cell(1, 2).Range.Text = "标准编号";

　　有一篇文章写的很详细可以参考下：https://www.cnblogs.com/xh6300/p/5915717.html

public bool CreateWord(DataTable dttmp)
        {
            bool result = false;
            Object Nothing = Missing.Value;
            Microsoft.Office.Interop.Word.Application application = new Microsoft.Office.Interop.Word.Application();
            Microsoft.Office.Interop.Word.Document document = null;
            string path = @"C:\Users\Administrator\Desktop\BB\合同模版.doc";
            object FileName = @"C:\Users\Administrator\Desktop\BB\" + DateTime.Now.ToString("yyyyMMddHHmmssffffff") + ".doc";
            application.Visible = false;
            document = application.Documents.Open(path);

            int rowNum = dttmp.Rows.Count;
            for (int i = 1; i <= document.Paragraphs.Count; i++)
            {
                string temptext = document.Paragraphs[i].Range.Text;
                //以下为替换文档模版中的关键字
                if (temptext.Contains("{$village}"))
                    document.Paragraphs[i].Range.Text = temptext.Replace("{$village}", "HELLO WORLD");
                Microsoft.Office.Interop.Word.Table table1 = document.Tables[1];
                table1.Cell(1, 1).Range.Text = "TEST1";
                if (temptext.Contains("{$Table1}"))
                {
                    //设置表格的行数和列数
                    int tableRow = 6 + rowNum;
                    int tableColumn = 13;
                    //定义一个Word中的表格对象
                   

                    Microsoft.Office.Interop.Word.Table table = document.Tables.Add(document.Paragraphs[i].Range,
                      tableRow, tableColumn, ref Nothing, ref Nothing);
                    //默认创建的表格没有边框，这里修改其属性，使得创建的表格带有边框 
                     table.Borders.Enable = 1;//这个值可以设置得很大
                     table.Cell(1, 1).Merge(table.Cell(2, 1));//纵向合并
                     table.Cell(1, 1).Range.Text = "牌号/代码";

                     table.Cell(1, 2).Merge(table.Cell(2, 2));//纵向合并
                     table.Cell(1, 2).Range.Text = "标准编号";

                 

                     table.Cell(1, 6).Merge(table.Cell(2, 6));
                     table.Cell(1, 6).Range.Text = "单重\n(MT)";

                     table.Cell(1, 7).Merge(table.Cell(2, 7));
                     table.Cell(1, 7).Range.Text = "张数";
                     
                     table.Cell(1, 8).Merge(table.Cell(2, 8));
                     table.Cell(1, 8).Range.Text = "重量\n(MT))";
                  
                     

                     table.Cell(1, 9).Merge(table.Cell(2, 9));
                     table.Cell(1, 9).Range.Text = "单价\n(元/吨)";
                                        
                     table.Cell(1, 10).Merge(table.Cell(2, 10));
                     table.Cell(1, 10).Range.Text = "金额(人民币)";
                                      
         
                     table.Cell(1, 13).Merge(table.Cell(2, 13));
                     table.Cell(1, 13).Range.Text = "交货期";

                     table.Cell(1, 3).Merge(table.Cell(1, 5));//横向合并
                     table.Cell(1, 3).Range.Text = "规格(mm)";
                     table.Cell(2, 3).Range.Text = "厚度";
                     table.Cell(2, 4).Range.Text = "宽度";
                     table.Cell(2, 5).Range.Text = "宽度";

                     table.Cell(1, 9).Merge(table.Cell(1, 10));
                     table.Cell(1, 10).Range.Text = "表面加工";
                     table.Cell(2, 11).Range.Text = "边缘";
                     table.Cell(2, 11).Range.Text = "精度";
                
                }
            }
           
            object format = document.SaveFormat;
            document.Save();

            application.Quit(ref Nothing, ref Nothing, ref Nothing);
            return result;

        }

 public bool WordToPDF(string sourcePath)
        {
            bool result = false;
           Microsoft.Office.Interop.Word.Application application = new Microsoft.Office.Interop.Word.Application();
            Microsoft.Office.Interop.Word.Document document = null;
            try
            {
                application.Visible = false;
                document = application.Documents.Open(sourcePath);
                string PDFPath = sourcePath.Replace(".doc", ".pdf");//pdf存放位置
                if (!File.Exists(@PDFPath))//存在PDF，不需要继续转换
                {
                    document.ExportAsFixedFormat(PDFPath, Microsoft.Office.Interop.Word.WdExportFormat.wdExportFormatPDF);
                }
                result = true;
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                result = false;
            }
            finally
            {
                //document.Close();
            }
            return result;
        }