Insert text watermark in PDF

C#/VB.NET: stay PDF Insert a text watermark into the document

A watermark is a text or image that appears before or after existing content in a document . It is usually used to prevent documents from being used illegally . Next , I'll show you how to use

 Spire.PDF for .NET

 

stay  C# and VB.NET  In the procedure is PDF Add one or more lines of text watermark to the document .

 

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by PDF Add a single line text watermark

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by PDF Add multi line text watermark

 

install  Spire.PDF for .NET

First , We need to  Spire.PDF for .NET  The package contains  DLL  Add file as  .NET  References in the project . It can be downloaded from

This link

download  DLL  file , It can also be done through  

NuGet

  install  DLL  file .

 

PM> Install-Package Spire.PDF

 

by PDF Add a single line text watermark

using Spire.Pdf;
using Spire.Pdf.Graphics;
using System.Drawing;
 
namespace AddTextWatermarkToPdf
{
 class Program
 {
 static void Main(string[] args)
 {
 // establish PdfDocument Class object
 PdfDocument pdf = new PdfDocument();
 
 // Load one PDF Document instance
 pdf.LoadFromFile(@"sample.pdf");
 
 // establish PdfTrueTypeFont Class object
 PdfTrueTypeFont font = new PdfTrueTypeFont(new Font(" Song style ", 55f), true);
 
 // Set the text content of the watermark
 string text = " Please don't embezzle ";
 
 // Set the text watermark size
 SizeF textSize = font.MeasureString(text);
 
 // Calculate the value of two offset variables , Used to calculate the translation of the coordinate system
 float offset1 = (float)(textSize.Width * System.Math.Sqrt(2) / 4);
 float offset2 = (float)(textSize.Height * System.Math.Sqrt(2) / 4);
 
 // Traverse all pages in the document
 foreach (PdfPageBase page in pdf.Pages)
 {
 // Set page transparency
 page.Canvas.SetTransparency(0.8f);
 
 // Translate the coordinate system to the lower right corner
 page.Canvas.TranslateTransform(page.Canvas.Size.Width / 2 - offset1 - offset2, page.Canvas.Size.Height / 2 + offset1 - offset2);
 
 // Rotate the coordinate system counterclockwise 45 degree
 page.Canvas.RotateTransform(-45);
 
 // Draw a text watermark on the page
 page.Canvas.DrawString(text, font, PdfBrushes.DarkGray, 0, 0);
 }
 
 // Save changes to another file
 pdf.SaveToFile("TextWatermark.pdf");
 }
 }
}


VB.NET

Imports Spire.Pdf
Imports Spire.Pdf.Graphics
Imports System.Drawing
 
Namespace AddTextWatermarkToPdf
 Class Program
 Shared Sub Main(ByVal args() As String)
 ' establish PdfDocument Class object
 Dim pdf As PdfDocument = New PdfDocument() 
 
 ' Load one PDF Document instance
 pdf.LoadFromFile("C: sample.pdf")
 
 ' establish PdfTrueTypeFont Class object
 Dim font As PdfTrueTypeFont = New PdfTrueTypeFont(New Font(" Song style ",55f),True) 
 
 ' Set the text content of the watermark
 Dim text As String = " Please don't embezzle "
 
 ' Set the text watermark size
 Dim textSize As SizeF = font.MeasureString(text) 
 
 ' Calculate the value of two offset variables , Used to calculate the translation of the coordinate system
 Dim offset1 As single = CType((textSize.Width * System.Math.Sqrt(2) / 4), single)
 Dim offset2 As single = CType((textSize.Height * System.Math.Sqrt(2) / 4), single)
 
 ' Traverse all pages in the document
 Dim page As PdfPageBase
 For Each page In pdf.Pages
 ' Set page transparency
 page.Canvas.SetTransparency(0.8f)
 
 ' Translate the coordinate system to the lower right corner
 page.Canvas.TranslateTransform(page.Canvas.Size.Width / 2 - offset1 - offset2, page.Canvas.Size.Height / 2 + offset1 - offset2)
 
 ' Rotate the coordinate system counterclockwise 45 degree
 page.Canvas.RotateTransform(-45)
 
 ' Add a text watermark on the page
 page.Canvas.DrawString(text, font, PdfBrushes.DarkGray, 0, 0)
 Next
 
 ' Save changes to another file
 pdf.SaveToFile("TextWatermark.pdf")
 End Sub
 End Class
End Namespace


by PDF Add multi line text watermark

using System;
using Spire.Pdf;
using Spire.Pdf.Graphics;
using System.Drawing;
 
namespace AddMultiLineTextWatermark
{
 class Program
 {
 static void Main(string[] args)
 {
 // establish PdfDocument Class object
 PdfDocument pdf = new PdfDocument();
 
 // Load one PDF file
 pdf.LoadFromFile(@"sample.pdf");
 
 // establish PdfTrueTypeFont Class object
 PdfTrueTypeFont font = new PdfTrueTypeFont(new Font(" Song style ", 20f), true);
 
 // Traverse document pages
 for (int i = 0; i < pdf.Pages.Count; i++)
 {
 // Add a text watermark on a specific page
 InsertTextWatermark(pdf.Pages[i], &quot; Do not copy &quot;, font, 3, 3);
 }
 
 // Save the file
 pdf.SaveToFile(&quot;MultiLineTextWaterMark.pdf&quot;);
 System.Diagnostics.Process.Start(&quot;MultiLineTextWaterMark.pdf&quot;);
 }
 
 static void InsertTextWatermark(PdfPageBase page, String watermarkText, PdfTrueTypeFont font, int rowNum, int columnNum)
 {
 
 // Set the text watermark size
 SizeF textSize = font.MeasureString(watermarkText);
 
 // Calculate the value of two offset variables , Used to calculate the translation of the coordinate system
 float offset1 = (float)(textSize.Width * System.Math.Sqrt(2) / 4);
 float offset2 = (float)(textSize.Height * System.Math.Sqrt(2) / 4);
 
 // Create a tile brush
 PdfTilingBrush brush = new PdfTilingBrush(new SizeF(page.ActualSize.Width / columnNum, page.ActualSize.Height / rowNum));
 brush.Graphics.SetTransparency(0.5f);
 brush.Graphics.Save();
 brush.Graphics.TranslateTransform(brush.Size.Width / 2 - offset1 - offset2, brush.Size.Height / 2 + offset1 - offset2);
 brush.Graphics.RotateTransform(-45);
 
 // Draw a text watermark on the tile brush
 brush.Graphics.DrawString(watermarkText, font, PdfBrushes.Violet, 0, 0);
 brush.Graphics.Restore();
 
 // Use the tile brush to draw a rectangle covering the entire page
 page.Canvas.DrawRectangle(brush, new RectangleF(new PointF(0, 0), page.ActualSize));
 }
 }
}


VB.NET

Imports System
Imports Spire.Pdf
Imports Spire.Pdf.Graphics
Imports System.Drawing
 
Namespace AddMultiLineTextWatermark
 Class Program
 Shared Sub Main(ByVal args() As String)
 ' establish PdfDocument Class object
 Dim pdf As PdfDocument = New PdfDocument() 
 
 ' Load one PDF file
 pdf.LoadFromFile("sample.pdf")
 
 ' establish PdfTrueTypeFont Class object
 Dim font As PdfTrueTypeFont = New PdfTrueTypeFont(New Font(" Song style ",20f),True) 
 
 ' Traverse document pages
 Dim i As Integer
 For i = 0 To pdf.Pages.Count- 1 Step i + 1
 ' Add a text watermark on a specific page
 InsertTextWatermark(pdf.Pages(i), " Do not copy ", font, 3, 3)
 Next
 
 ' Save the file
 pdf.SaveToFile("MultiLineTextWaterMark.pdf")
 System.Diagnostics.Process.Start("MultiLineTextWaterMark.pdf")
 End Sub
 
 Shared Sub InsertTextWatermark(ByVal page As PdfPageBase, ByVal watermarkText As String, ByVal font As PdfTrueTypeFont, ByVal rowNum As Integer, ByVal columnNum As Integer)
 
 ' Set the text watermark size
 Dim textSize As SizeF = font.MeasureString(watermarkText) 
 
 ' Calculate the value of two offset variables , Used to calculate the translation of the coordinate system  
float offset1 = (float)(textSize.Width * System.Math.Sqrt(2) / 4);
 float offset2 = (float)(textSize.Height * System.Math.Sqrt(2) / 4);
 
 ' Create a tile brush
 Dim brush As PdfTilingBrush = New PdfTilingBrush(New SizeF(page.ActualSize.Width / columnNum,page.ActualSize.Height / rowNum)) 
 brush.Graphics.SetTransparency(0.5f)
 brush.Graphics.Save()
 brush.Graphics.TranslateTransform(brush.Size.Width / 2 - offset1 - offset2, brush.Size.Height / 2 + offset1 - offset2)
 brush.Graphics.RotateTransform(-45)
 
 ' Draw a text watermark on the tile brush

 brush.Graphics.DrawString(watermarkText, font, PdfBrushes.Violet, 0, 0)
 brush.Graphics.Restore()
 
 ' Use the tile brush to draw a rectangle covering the entire page
 page.Canvas.DrawRectangle(brush, New RectangleF(New PointF(0, 0), page.ActualSize))
 End Sub
 End Class
End Namespace