watermarking a word document using OpenXML sdk

Question

I followed the watermarking code given below:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using DocumentFormat.OpenXml;
using DocumentFormat.OpenXml.Packaging;
using DocumentFormat.OpenXml.Vml;
using DocumentFormat.OpenXml.Vml.Office;
using DocumentFormat.OpenXml.Vml.Wordprocessing;
using DocumentFormat.OpenXml.Wordprocessing;
using HorizontalAnchorValues = DocumentFormat.OpenXml.Vml.Wordprocessing.HorizontalAnchorValues;
using Lock = DocumentFormat.OpenXml.Vml.Office.Lock;
using VerticalAnchorValues = DocumentFormat.OpenXml.Vml.Wordprocessing.VerticalAnchorValues;

namespace DocumentWatermarkTest
{
    class Program
    {
        static void Main(string[] args)
        {
            byte[] sourceBytes = File.ReadAllBytes(@"C:\Users\loggedinuser\Desktop\TestDoc.docx");

            MemoryStream inMemoryStream = new MemoryStream();
            inMemoryStream.Write(sourceBytes, 0, (int)sourceBytes.Length);

            var doc = WordprocessingDocument.Open(inMemoryStream, true);
            AddWatermark(doc);
            doc.MainDocumentPart.Document.Save();

            doc.Close();
            doc.Dispose();
            doc = null;

            using (FileStream fileStream = new FileStream(@"C:\Users\loggedinuser\Desktop\TestDoc.docx", System.IO.FileMode.Create))
            {
                inMemoryStream.WriteTo(fileStream);
            }

            inMemoryStream.Close();
            inMemoryStream.Dispose();
            inMemoryStream = null;
        }

        static Header MakeHeader()
        {
            var header = new Header();
            var paragraph = new Paragraph();
            var run = new Run();
            var text = new Text();
            text.Text = "";
            run.Append(text);
            paragraph.Append(run);
            header.Append(paragraph);
            return header;
        }

        static void AddWatermark(WordprocessingDocument doc)
        {
            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 DocPartObjectSdt();
                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 = DocumentFormat.OpenXml.Vml.BooleanValues.True,
                    ConnectionPointType = ConnectValues.Custom,
                    ConnectionPoints = "@9,0;@10,10800;@11,21600;@12,10800",
                    ConnectAngles = "270,180,90,0"
                };
                var textPath1 = new TextPath()
                {
                    On = DocumentFormat.OpenXml.Vml.BooleanValues.True,
                    FitShape = DocumentFormat.OpenXml.Vml.BooleanValues.True
                };
                var shapeHandles1 = new Handles();

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

                shapeHandles1.Append(shapeHandle1);

                var lock1 = new Lock
                {
                    Extension = ExtensionHandlingBehaviorValues.Edit,
                    TextLock = DocumentFormat.OpenXml.Vml.Office.BooleanValues.True,
                    ShapeType = DocumentFormat.OpenXml.Vml.Office.BooleanValues.True
                };

                shapetype1.Append(formulas1);
                shapetype1.Append(path1);
                shapetype1.Append(textPath1);
                shapetype1.Append(shapeHandles1);
                shapetype1.Append(lock1);
                var shape1 = new Shape()
                                 {
                                     Id = "PowerPlusWaterMarkObject357476642",
                                     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 = DocumentFormat.OpenXml.Vml.BooleanValues.False,
                                     FillColor = "silver",
                                     Stroked = DocumentFormat.OpenXml.Vml.BooleanValues.False,
                                     Type = "#_x0000_t136"
                                 };


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

                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;
            }
        }
    }
}

When I use this code, the watermarked text lies below the actual contents of the word document. If there are images in the word document, the watermarked text gets hidden completely and is not visible. Can I somehow place the watermarked text on top of the contents of the word document? Any help would be really appreciated.