How to add a watermark in the center of the page in a PDF document using C# and VB.NET?

6 mins read

The Syncfusion Essential® PDF is a .NET PDF library used to create, read, and edit PDF documents. Using this library, you can add a watermark in the center of the page in a PDF document using C# and VB.NET.

Steps to add a watermark in the center of the page in a PDF document

Create a new Windows Forms application project.

Create Windows Forms application project

Install the Syncfusion.Pdf.WinForms NuGet package as a reference to your .NET Framework application from NuGet.org.

NuGet package reference

Include the following namespace in the Form1.cs file.

using Syncfusion.Pdf;
using Syncfusion.Pdf.Parsing;
using Syncfusion.Pdf.Graphics;
using System.Drawing;

VB.NET

Imports Syncfusion.Pdf
Imports Syncfusion.Pdf.Parsing
Imports Syncfusion.Pdf.Graphics
Imports System.Drawing

Add the following code in the button1_click event to add a watermark in the center of the page in a PDF document using C# and VB.NET.

//Load an existing PDF document 
PdfLoadedDocument loadedDocument = new PdfLoadedDocument("../../Data/Barcode.pdf");
 
//Set the font
PdfFont font = new PdfStandardFont(PdfFontFamily.Helvetica, 20);
 
string watermarkText = "Imported using Essential PDF";
 
//Calculate the watermark text size
SizeF size = font.MeasureString(watermarkText);
 
for (int i=0;i<loadedDocument.Pages.Count;i++)
{
    //Load PDF pages
    PdfLoadedPage loadedPage = loadedDocument.Pages[i] as PdfLoadedPage;
 
    //Create graphics for the existing page
    PdfGraphics graphics = loadedPage.Graphics;
 
    float x = loadedPage.Size.Width / 2 - size.Width / 2;
    float y = loadedPage.Size.Height / 2;
 
    //Insert watermark text to PDF 
    PdfGraphicsState state = graphics.Save();
    graphics.SetTransparency(0.25f);
    graphics.DrawString(watermarkText, font, PdfBrushes.Red, new RectangleF(x, y, size.Width, size.Height));
    graphics.Restore();
 
    //Draw string 
    graphics.DrawString("Hello World!!!", font, PdfBrushes.Black, new PointF(0, 0));
}
 
//Save and close the document
loadedDocument.Save("Watermark.pdf");
loadedDocument.Close(true);
 
//This will open the PDF file and the result will be seen in the default PDF Viewer
Process.Start("Watermark.pdf");

VB.NET

'Load an existing PDF document  
Dim loadedDocument As PdfLoadedDocument = New PdfLoadedDocument("../../Data/Barcode.pdf")
 
'Set the font 
Dim font As PdfFont = New PdfStandardFont(PdfFontFamily.Helvetica, 20)
 
Dim watermarkText As String = "Imported using Essential PDF"
 
'Calculate the watermark text size 
Dim size As SizeF = font.MeasureString(watermarkText)
 
For i As Integer = 0 To loadedDocument.Pages.Count - 1
 
    'Load PDF pages 
    Dim loadedPage As PdfLoadedPage = TryCast(loadedDocument.Pages(i), PdfLoadedPage)
 
    'Create graphics for the existing page 
    Dim graphics As PdfGraphics = loadedPage.Graphics
 
    Dim x As Single = loadedPage.Size.Width / 2 - size.Width / 2
    Dim y As Single = loadedPage.Size.Height / 2
 
    'Insert watermark text to PDF  
    Dim state As PdfGraphicsState = graphics.Save()
    graphics.SetTransparency(0.25F)
    graphics.DrawString(watermarkText, font, PdfBrushes.Red, New RectangleF(x, y, size.Width, size.Height))
    graphics.Restore()
 
    'Draw string  
    graphics.DrawString("Hello World!!!", font, PdfBrushes.Black, New PointF(0, 0))
 
Next
 
'Save and close the document 
loadedDocument.Save("Watermark.pdf")
loadedDocument.Close(True)
 
'This will open the PDF file and the result will be seen in the default PDF Viewer
Process.Start("Watermark.pdf")

A complete working sample can be download from WatermarkSample.zip.

By executing the program, you will get the output document as follows,

Output document screenshot

Take a moment to peruse the documentation. You can find other options like adding image watermark in PDF document and features like images to PDF, Text to PDF, and more with code examples.

Refer to here to explore a rich set of Syncfusion Essential® PDF features.

Note:

Starting with v16.2.0.x, if you reference Syncfusion® assemblies from the trial setup or the NuGet feed, include a license key in your projects. Refer to the link to learn about generating and registering the Syncfusion® license key in your application to use the components without a trial message.

How to add a watermark in the center of the page in a PDF document using C# and VB.NET?

Steps to add a watermark in the center of the page in a PDF document

Access denied