static void AddWatermark(WordprocessingDocument doc, string textWatermark)
        {
            if (doc.MainDocumentPart.HeaderParts.Count() == 0)
            {
                doc.MainDocumentPart.DeleteParts(doc.MainDocumentPart.HeaderParts);
                var newHeaderPart = doc.MainDocumentPart.AddNewPart <HeaderPart>();
                var rId           = doc.MainDocumentPart.GetIdOfPart(newHeaderPart);
                var headerRef     = new HeaderReference();
                headerRef.Id = rId;
                var sectionProps = doc.MainDocumentPart.Document.Body.Elements <SectionProperties>().LastOrDefault();
                if (sectionProps == null)
                {
                    sectionProps = new SectionProperties();
                    doc.MainDocumentPart.Document.Body.Append(sectionProps);
                }
                sectionProps.RemoveAllChildren <HeaderReference>();
                sectionProps.Append(headerRef);

                newHeaderPart.Header = MakeHeader();
                newHeaderPart.Header.Save();
            }

            foreach (HeaderPart headerPart in doc.MainDocumentPart.HeaderParts)
            {
                var sdtBlock1      = new SdtBlock();
                var sdtProperties1 = new SdtProperties();
                var sdtId1         = new SdtId()
                {
                    Val = 87908844
                };
                var sdtContentDocPartObject1 = new SdtContentDocPartObject();
                var docPartGallery1          = new DocPartGallery()
                {
                    Val = "Watermarks"
                };
                var docPartUnique1 = new DocPartUnique();
                sdtContentDocPartObject1.Append(docPartGallery1);
                sdtContentDocPartObject1.Append(docPartUnique1);
                sdtProperties1.Append(sdtId1);
                sdtProperties1.Append(sdtContentDocPartObject1);

                var sdtContentBlock1 = new SdtContentBlock();
                var paragraph2       = new Paragraph()
                {
                    RsidParagraphAddition  = "00656E18",
                    RsidRunAdditionDefault = "00656E18"
                };
                var paragraphProperties2 = new ParagraphProperties();
                var paragraphStyleId2    = new ParagraphStyleId()
                {
                    Val = "Header"
                };
                paragraphProperties2.Append(paragraphStyleId2);
                var run1           = new Run();
                var runProperties1 = new RunProperties();
                var noProof1       = new NoProof();
                var languages1     = new Languages()
                {
                    EastAsia = "zh-TW"
                };
                runProperties1.Append(noProof1);
                runProperties1.Append(languages1);
                var picture1   = new Picture();
                var shapetype1 = new Shapetype()
                {
                    Id             = "_x0000_t136",
                    CoordinateSize = "21600,21600",
                    OptionalNumber = 136,
                    Adjustment     = "10800",
                    EdgePath       = "m@7,l@8,m@5,21600l@6,21600e"
                };
                var formulas1 = new Formulas();
                var formula1  = new Formula()
                {
                    Equation = "sum #0 0 10800"
                };
                var formula2 = new Formula()
                {
                    Equation = "prod #0 2 1"
                };
                var formula3 = new Formula()
                {
                    Equation = "sum 21600 0 @1"
                };
                var formula4 = new Formula()
                {
                    Equation = "sum 0 0 @2"
                };
                var formula5 = new Formula()
                {
                    Equation = "sum 21600 0 @3"
                };
                var formula6 = new Formula()
                {
                    Equation = "if @0 @3 0"
                };
                var formula7 = new Formula()
                {
                    Equation = "if @0 21600 @1"
                };
                var formula8 = new Formula()
                {
                    Equation = "if @0 0 @2"
                };
                var formula9 = new Formula()
                {
                    Equation = "if @0 @4 21600"
                };
                var formula10 = new Formula()
                {
                    Equation = "mid @5 @6"
                };
                var formula11 = new Formula()
                {
                    Equation = "mid @8 @5"
                };
                var formula12 = new Formula()
                {
                    Equation = "mid @7 @8"
                };
                var formula13 = new Formula()
                {
                    Equation = "mid @6 @7"
                };
                var formula14 = new Formula()
                {
                    Equation = "sum @6 0 @5"
                };

                formulas1.Append(formula1);
                formulas1.Append(formula2);
                formulas1.Append(formula3);
                formulas1.Append(formula4);
                formulas1.Append(formula5);
                formulas1.Append(formula6);
                formulas1.Append(formula7);
                formulas1.Append(formula8);
                formulas1.Append(formula9);
                formulas1.Append(formula10);
                formulas1.Append(formula11);
                formulas1.Append(formula12);
                formulas1.Append(formula13);
                formulas1.Append(formula14);
                var path1 = new Path()
                {
                    AllowTextPath       = TrueFalseValue.FromBoolean(true),
                    ConnectionPointType = ConnectValues.Custom,
                    ConnectionPoints    = "@9,0;@10,10800;@11,21600;@12,10800",
                    ConnectAngles       = "270,180,90,0"
                };
                var textPath1 = new TextPath()
                {
                    On       = TrueFalseValue.FromBoolean(true),
                    FitShape = TrueFalseValue.FromBoolean(true)
                };
                var shapeHandles1 = new ShapeHandles();

                var shapeHandle1 = new ShapeHandle()
                {
                    Position = "#0,bottomRight",
                    XRange   = "6629,14971"
                };

                shapeHandles1.Append(shapeHandle1);

                var lock1 = new Lock
                {
                    Extension = ExtensionHandlingBehaviorValues.Edit,
                    TextLock  = TrueFalseValue.FromBoolean(true),
                    ShapeType = TrueFalseValue.FromBoolean(true)
                };

                shapetype1.Append(formulas1);
                shapetype1.Append(path1);
                shapetype1.Append(textPath1);
                shapetype1.Append(shapeHandles1);
                shapetype1.Append(lock1);
                var shape1 = new Shape()
                {
                    Id             = "PowerPlusWaterMarkObject357922611",
                    Style          = "position:absolute;left:0;text-align:left;margin-left:0;margin-top:0;width:527.85pt;height:131.95pt;rotation:315;z-index:-251656192;mso-position-horizontal:center;mso-position-horizontal-relative:margin;mso-position-vertical:center;mso-position-vertical-relative:margin",
                    OptionalString = "_x0000_s2049",
                    AllowInCell    = TrueFalseValue.FromBoolean(true),
                    FillColor      = "silver",
                    Stroked        = TrueFalseValue.FromBoolean(false),
                    Type           = "#_x0000_t136"
                };


                var fill1 = new Fill()
                {
                    Opacity = ".5"
                };
                TextPath textPath2 = new TextPath()
                {
                    Style  = "font-family:\"Calibri\";font-size:1pt",
                    String = textWatermark
                };

                var textWrap1 = new TextWrap()
                {
                    AnchorX = HorizontalAnchorValues.Margin,
                    AnchorY = VerticalAnchorValues.Margin
                };

                shape1.Append(fill1);
                shape1.Append(textPath2);
                shape1.Append(textWrap1);
                picture1.Append(shapetype1);
                picture1.Append(shape1);
                run1.Append(runProperties1);
                run1.Append(picture1);
                paragraph2.Append(paragraphProperties2);
                paragraph2.Append(run1);
                sdtContentBlock1.Append(paragraph2);
                sdtBlock1.Append(sdtProperties1);
                sdtBlock1.Append(sdtContentBlock1);
                headerPart.Header.Append(sdtBlock1);
                headerPart.Header.Save();
                //break;
            }
        }