Using VB.NET PDF SDK Library
How to create, edit, update, remove PDF file annotations and drawings using VB.NET

Dim inputFilePath As String = Program.RootPath + "\\" + "1_Annots.pdf"

Dim doc As PDFDocument = New PDFDocument(inputFilePath)
Dim annots = PDFAnnotHandler.GetAllAnnotations(doc)

Console.WriteLine("Number of Annotations: " + annots.Count)
If annots.Count > 0 Then
    For Each annot As IPDFAnnot In annots
        Console.WriteLine("Annotation")
        Console.WriteLine("  Page:     " + annot.PageIndex)
        Console.WriteLine("  Aritst:   " + annot.Artist)
        Console.WriteLine("  Subject:  " + annot.Subject)
        Console.WriteLine("  Content:  " + annot.Content)
    Next
End If

Dim inputFilePath As String = Program.RootPath + "\\" + "1_Annots.pdf"

Dim doc As PDFDocument = New PDFDocument(inputFilePath)
Dim page As PDFPage = doc.GetPage(0)
Dim annots = PDFAnnotHandler.GetAllAnnotations(page)

Dim inputFilePath As String = "C:\1_Annots.pdf"

Dim doc As PDFDocument = New PDFDocument(inputFilePath)
' get all annotations in the 1st page
Dim page As PDFPage = doc.GetPage(0)
Dim annots = PDFAnnotHandler.GetAllAnnotations(page)
' remove all annotations in the 1st page
PDFAnnotHandler.DeleteAnnotation(doc, annots)

Dim inputFilePath As String = "C:\Annot_1.pdf"

Dim doc As PDFDocument = New PDFDocument(inputFilePath)
Dim annots As List(Of IPDFAnnot) = PDFAnnotHandler.GetAllAnnotations(doc)
For Each annot As IPDFAnnot In annots
    If TypeOf annot Is IPDFPopupAnnot Then
        Console.WriteLine("Annotation has popup window")

        Dim obj As IPDFPopupAnnot = annot
        Console.WriteLine("Is open in the begin:  {0}", obj.Popup.IsOpen)
        Console.WriteLine("Popup window boundary: {0}", obj.Popup.Boundary.ToString())
    Else
        Console.WriteLine("Annotation has no popup window")
    End If
Next

Dim inputFilePath As String = "C:\Annot_1.pdf"

Dim doc As PDFDocument = New PDFDocument(inputFilePath)
Dim annots As List(Of IPDFAnnot) = PDFAnnotHandler.GetAllAnnotations(doc)
For Each annot As IPDFAnnot In annots
    Console.WriteLine("Annotation Flags")
    Console.WriteLine("  Invisible:       {0}", annot.IsInvisible)
    Console.WriteLine("  Hidden:          {0}", annot.IsHidden)
    Console.WriteLine("  Print:           {0}", annot.IsPrint)
    Console.WriteLine("  No Zoom:         {0}", annot.NoZoom)
    Console.WriteLine("  No Rotate:       {0}", annot.NoRotate)
    Console.WriteLine("  No View:         {0}", annot.NoView)
    Console.WriteLine("  Read Only:       {0}", annot.IsReadOnly)
    Console.WriteLine("  Locked:          {0}", annot.IsLocked)
    Console.WriteLine("  Toggle No View:  {0}", annot.IsToggleNoView)
    Console.WriteLine("  Locked Contents: {0}", annot.IsLockedContents)
Next

Dim inputFilePath As String = "C:\2.pdf"
Dim outputFilePath As String = "C:\Annot_1.pdf"

' create the annotation
Dim annot As PDFAnnotDeleteLine = New PDFAnnotDeleteLine()
annot.StartPoint = New PointF(100.0F, 200.0F)
annot.EndPoint = New PointF(300.0F, 400.0F)

' set annotation flags
annot.IsInvisible = False
annot.IsPrint = True
annot.NoRotate = True
annot.NoZoom = True

' add annotation
PDFAnnotHandler.AddAnnotation(inputFilePath, 1, annot, outputFilePath)