The example demonstrates how to add a text annotation using ByteScout PDF SDK.

Program.vb:
VB

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

Imports Bytescout.PDF

''' <summary>
''' This example demonstrates how to add a text annotation.
''' </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)

        ' Add collapsed annotation (shown as a tooltip when mouse is over the icon)
        Dim collapsedAnnotation = New TextAnnotation(20, 20)
        collapsedAnnotation.Color = New ColorRGB(255, 255, 0)
        collapsedAnnotation.Icon = TextAnnotationIcon.Comment
        collapsedAnnotation.Author = "Mr. Important"
        collapsedAnnotation.Contents = "The quick brown fox jumps over the lazy dog."
        page.Annotations.Add(collapsedAnnotation)

        ' Add expanded annotation
        Dim expandedAnnotation = New TextAnnotation(20, 50)
        expandedAnnotation.Color = New ColorRGB(255, 0, 0)
        expandedAnnotation.Icon = TextAnnotationIcon.Note
        expandedAnnotation.Open = True
        expandedAnnotation.Author = "John Doe"
        expandedAnnotation.Contents = "The quick brown fox jumps over the lazy dog."
        page.Annotations.Add(expandedAnnotation)

        ' 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 - http://www.bytescout.com       
//       ALL RIGHTS RESERVED                                         
//                                                                   
//*******************************************************************

using System.Diagnostics;
using Bytescout.PDF;

namespace TextAnnotationExample
{
	/// <summary>
	/// This example demonstrates how to add a text annotation.
	/// </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);

			// Add collapsed annotation (shown as a tooltip when mouse is over the icon)
			TextAnnotation collapsedAnnotation = new TextAnnotation(20, 20);
			collapsedAnnotation.Color = new ColorRGB(255, 255, 0);
			collapsedAnnotation.Icon = TextAnnotationIcon.Comment;
			collapsedAnnotation.Author = "Mr. Important";
			collapsedAnnotation.Contents = "The quick brown fox jumps over the lazy dog.";
			page.Annotations.Add(collapsedAnnotation);

			// Add expanded annotation
			TextAnnotation expandedAnnotation = new TextAnnotation(20, 50);
			expandedAnnotation.Color = new ColorRGB(255, 0, 0);
			expandedAnnotation.Icon = TextAnnotationIcon.Note;
			expandedAnnotation.Open = true;
			expandedAnnotation.Author = "John Doe";
			expandedAnnotation.Contents = "The quick brown fox jumps over the lazy dog.";
			page.Annotations.Add(expandedAnnotation);
			
			// Save document to file
			pdfDocument.Save("result.pdf");

			// Cleanup 
			pdfDocument.Dispose();

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