How to add semitransparent text watermarks to existing PDF document using ByteScout PDF SDK

How to add text watermarks into existing PDF document
This example demonstrates how to add backround semi-transparent text watermarks into existing PDF documents

Program.vb:
VB

'*******************************************************************
'       ByteScout PDF SDK
'                                                                   
'       Copyright © 2016 Bytescout, https://bytescout.com        
'       ALL RIGHTS RESERVED                                         
'                                                                   
'*******************************************************************

Imports Bytescout.PDF

''' <summary>
''' This example demonstrates how to draw transparent objects.
''' </summary>
Class Program

    Shared Sub Main()

        ' Create new document
        Dim pdfDocument = New Document()
        pdfDocument.RegistrationName = "demo"
		pdfDocument.RegistrationKey = "demo"
        ' Add page
        Dim page = New Page(PaperFormat.A4)
        pdfDocument.Pages.Add(page)

        Dim canvas = page.Canvas

        ' Prepare pens and brushes
        Dim borderPen = New SolidPen(New ColorRGB(0, 0, 0), 2.0F)

        Dim brush1 = New SolidBrush(New ColorRGB(255, 0, 0))
        Dim brush2 = New SolidBrush(New ColorRGB(0, 0, 255))

        borderPen.Opacity = 50
        brush1.Opacity = 30
        brush2.Opacity = 60

        ' Draw normal rectangles
        canvas.DrawRectangle(brush1, 100, 100, 100, 100)
        canvas.DrawRectangle(borderPen, brush2, 150, 150, 100, 100)

        borderPen.Opacity = 80
        brush1.Opacity = 60
        brush2.Opacity = 30

        ' Draw rounded rectangles
        canvas.DrawRoundedRectangle(brush1, 220, 100, 100, 100, 10)
        canvas.DrawRoundedRectangle(borderPen, brush2, 270, 150, 100, 100, 10)

        ' Save document to file
        pdfDocument.Save("result.pdf")

        ' Cleanup 
		pdfDocument.Dispose()

        ' Open document in default PDF viewer app
        Process.Start("result.pdf")

    End Sub

End Class 

Program.cs:
C#

//*******************************************************************
//       ByteScout PDF SDK		                                     
//                                                                   
//       Copyright © 2016 ByteScout - https://bytescout.com       
//       ALL RIGHTS RESERVED                                         
//                                                                   
//*******************************************************************

using System.Diagnostics;
using Bytescout.PDF;

namespace Transparency
{
	/// <summary>
	/// This example demonstrates how to draw transparent objects.
	/// </summary>
	class Program
	{
		static void Main()
		{
			// Create new document
			Document pdfDocument = new Document();
			pdfDocument.RegistrationName = "demo";
			pdfDocument.RegistrationKey = "demo";
			// Add page
			Page page = new Page(PaperFormat.A4);
			pdfDocument.Pages.Add(page);

			Canvas canvas = page.Canvas;

			// Prepare pens and brushes
			Pen borderPen = new SolidPen(new ColorRGB(0, 0, 0), 2f);
			
			SolidBrush brush1 = new SolidBrush(new ColorRGB(255, 0, 0));
			SolidBrush brush2 = new SolidBrush(new ColorRGB(0, 0, 255));
			
			borderPen.Opacity = 50;
			brush1.Opacity = 30;
			brush2.Opacity = 60;

			// Draw normal rectangles
			canvas.DrawRectangle(brush1, 100, 100, 100, 100);
			canvas.DrawRectangle(borderPen, brush2, 150, 150, 100, 100);

			borderPen.Opacity = 80;
			brush1.Opacity = 60;
			brush2.Opacity = 30;

			// Draw rounded rectangles
			canvas.DrawRoundedRectangle(brush1, 220, 100, 100, 100, 10);
			canvas.DrawRoundedRectangle(borderPen, brush2, 270, 150, 100, 100, 10);
			
			// Save document to file
			pdfDocument.Save("result.pdf");

			// Cleanup 
			pdfDocument.Dispose();

			// Open document in default PDF viewer app
			Process.Start("result.pdf");
		}
	}
}