通常情况下，Microsoft word只支持添加一个文本水印到Word文档。该文将介绍如何使用Spire.Doc for .NET 在Word文档中页眉中添加艺术字模拟实现Word文档中多行文字水印效果。

using Spire.Doc;
using Spire.Doc.Documents;
using Spire.Doc.Fields;

namespace WordWatermark
{
    class Program
    {
        static void Main(string[] args)
        {
            //加载示例文档
            Document doc = new Document();
            doc.LoadFromFile("Sample.docx");

            //添加艺术字并设置大小
            ShapeObject shape = new ShapeObject(doc,ShapeType.TextPlainText);
            shape.Width = 60;
            shape.Height = 20;

            //设置艺术字文本内容、位置及样式
            shape.VerticalPosition = 30;
            shape.HorizontalPosition = 20;
            shape.Rotation = 315;
            shape.WordArt.Text = "内部使用";
            shape.WordArt.FontFamily="宋体";

            shape.FillColor = System.Drawing.Color.Red;
            shape.StrokeColor = System.Drawing.Color.Gray;

            Section section;
            HeaderFooter header;
            for (int n = 0; n < doc.Sections.Count; n++)
            {
                section = doc.Sections[n];
 
                //获取section的页眉
                header = section.HeadersFooters.Header;
                Paragraph paragraph1;
                for (int i = 0; i < 3; i++)
                {
                    //添加段落到页眉
                    paragraph1 = header.AddParagraph();
                    for (int j = 0; j < 4; j++)
                    {
                        //复制艺术字并设置多行多列位置
                        shape = (ShapeObject)shape.Clone();
                        shape.VerticalPosition = 50 + 150 * i;
                     
                        shape.HorizontalPosition=20 + 160 * j;
                        paragraph1.ChildObjects.Add(shape);
             
                    }
                }
            }
            //保存文档
            doc.SaveToFile("result.docx", FileFormat.Docx2013);
            System.Diagnostics.Process.Start("result.docx");
        }
    }
    
}

Class Program
    Private Shared Sub Main(ByVal args As String())
        Dim doc As Document = New Document()
        doc.LoadFromFile("Sample.docx")
        Dim shape As ShapeObject = New ShapeObject(doc, ShapeType.TextPlainText)
        shape.Width = 60
        shape.Height = 20
        shape.VerticalPosition = 30
        shape.HorizontalPosition = 20
        shape.Rotation = 315
        shape.WordArt.Text = "内部使用"
        shape.WordArt.FontFamily="宋体"
        
        shape.FillColor = System.Drawing.Color.Red
        shape.StrokeColor = System.Drawing.Color.Gray
        Dim section As Section
        Dim header As HeaderFooter

        For n As Integer = 0 To doc.Sections.Count - 1
            section = doc.Sections(n)
            header = section.HeadersFooters.Header
            Dim paragraph1 As Paragraph

            For i As Integer = 0 To 3 - 1
                paragraph1 = header.AddParagraph()

                For j As Integer = 0 To 4 - 1
                    shape = CType(shape.Clone(), ShapeObject)
                    shape.VerticalPosition = 50 + 150 * i
                    shape.HorizontalPosition = 20 + 160 * j
                    paragraph1.ChildObjects.Add(shape)
                Next
            Next
        Next
        doc.SaveToFile("result.docx", FileFormat.Docx2013)
    End Sub
End Class

多行多列文本水印效果图：