''' <summary>
''' Highlights specified text in PDF document.
''' </summary>
''' <param name="inputPdfFilename">The input PDF filename.</param>
''' <param name="outputPdfFilename">The output PDF filename.</param>
''' <param name="text">A text that must be highlighted.</param>
Public Shared Sub HiglightTextInPdfDocument(inputPdfFilename As String, outputPdfFilename As String, text As String)
    MarkupTextInPdfDocument(inputPdfFilename, outputPdfFilename, Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationType.Highlight, System.Drawing.Color.Orange, text)
End Sub

''' <summary>
''' Strikeouts specified text in PDF document.
''' </summary>
''' <param name="inputPdfFilename">The input PDF filename.</param>
''' <param name="outputPdfFilename">The output PDF filename.</param>
''' <param name="text">A text that must be striked out.</param>
Public Shared Sub StrikeoutTextInPdfDocument(inputPdfFilename As String, outputPdfFilename As String, text As String)
    MarkupTextInPdfDocument(inputPdfFilename, outputPdfFilename, Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationType.StrikeOut, System.Drawing.Color.Red, text)
End Sub

''' <summary>
''' Underlines specified text in PDF document.
''' </summary>
''' <param name="inputPdfFilename">The input PDF filename.</param>
''' <param name="outputPdfFilename">The output PDF filename.</param>
''' <param name="text">A text that must be underlined.</param>
Public Shared Sub UnderlineTextInPdfDocument(inputPdfFilename As String, outputPdfFilename As String, text As String)
    MarkupTextInPdfDocument(inputPdfFilename, outputPdfFilename, Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationType.Underline, System.Drawing.Color.Green, text)
End Sub

''' <summary>
''' Squiggly undeline specified text in PDF document.
''' </summary>
''' <param name="inputPdfFilename">The input PDF filename.</param>
''' <param name="outputPdfFilename">The output PDF filename.</param>
''' <param name="text">A text that must be squiggly underlined.</param>
Public Shared Sub SquigglyUnderlineTextInPdfDocument(inputPdfFilename As String, outputPdfFilename As String, text As String)
    MarkupTextInPdfDocument(inputPdfFilename, outputPdfFilename, Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationType.Squiggly, System.Drawing.Color.Blue, text)
End Sub

''' <summary>
''' Markups specified text in PDF document.
''' </summary>
''' <param name="inputPdfFilename">The input PDF filename.</param>
''' <param name="outputPdfFilename">The output PDF filename.</param>
''' <param name="color">The markup annotation color.</param>
''' <param name="annotationType">The markup annotation type.</param>
''' <param name="text">A text to markup.</param>
Private Shared Sub MarkupTextInPdfDocument(inputPdfFilename As String, outputPdfFilename As String, annotationType As Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationType, color As System.Drawing.Color, text As String)
    ' open input PDF document
    Using document As New Vintasoft.Imaging.Pdf.PdfDocument(inputPdfFilename)
        ' for each PDF page
        For Each page As Vintasoft.Imaging.Pdf.Tree.PdfPage In document.Pages
            ' extract text region of PDF page
            Dim pageTextRegion As Vintasoft.Imaging.Text.TextRegion = page.ExtractTextRegion(False)

            ' search and markup all specified text on PDF page
            Dim index As Integer = 0
            Dim foundText As Vintasoft.Imaging.Text.TextRegion
            While True
                ' find next text
                foundText = pageTextRegion.FindText(text, index, False)
                If foundText Is Nothing Then
                    Exit While
                End If
                index += foundText.Symbols.Length

                ' markup found text
                MarkupText(page, foundText, annotationType, color)
            End While
        Next

        ' save PDF document to output file
        document.SaveChanges(outputPdfFilename)
    End Using
End Sub

''' <summary>
''' Markups specified text region in PDF page.
''' </summary>
''' <param name="page">The page.</param>
''' <param name="textRegion">The text region to markup.</param>
''' <param name="color">The markup annotation color.</param>
''' <param name="annotationType">The markup annotation type.</param>
Private Shared Sub MarkupText(page As Vintasoft.Imaging.Pdf.Tree.PdfPage, textRegion As Vintasoft.Imaging.Text.TextRegion, annotationType As Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationType, color As System.Drawing.Color)
    ' create markup annotation of specified type
    Dim markupAnnotation As New Vintasoft.Imaging.Pdf.Tree.Annotations.PdfTextMarkupAnnotation(page, annotationType)

    ' set annotation properties
    markupAnnotation.SetArea(textRegion)
    markupAnnotation.Color = color
    markupAnnotation.Title = System.Environment.UserName
    markupAnnotation.CreationDate = System.DateTime.Now

    ' generate annotation appearance
    markupAnnotation.UpdateAppearance()

    ' add annotation to annotations of PDF page
    If page.Annotations Is Nothing Then
        page.Annotations = New Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationList(page.Document)
    End If
    page.Annotations.Add(markupAnnotation)
End Sub

/// <summary>
/// Highlights specified text in PDF document.
/// </summary>
/// <param name="inputPdfFilename">The input PDF filename.</param>
/// <param name="outputPdfFilename">The output PDF filename.</param>
/// <param name="text">A text that must be highlighted.</param>
public static void HiglightTextInPdfDocument(string inputPdfFilename, string outputPdfFilename, string text)
{
    MarkupTextInPdfDocument(inputPdfFilename, outputPdfFilename, Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationType.Highlight, System.Drawing.Color.Orange, text);
}

/// <summary>
/// Strikeouts specified text in PDF document.
/// </summary>
/// <param name="inputPdfFilename">The input PDF filename.</param>
/// <param name="outputPdfFilename">The output PDF filename.</param>
/// <param name="text">A text that must be striked out.</param>
public static void StrikeoutTextInPdfDocument(string inputPdfFilename, string outputPdfFilename, string text)
{
    MarkupTextInPdfDocument(inputPdfFilename, outputPdfFilename, Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationType.StrikeOut, System.Drawing.Color.Red, text);
}

/// <summary>
/// Underlines specified text in PDF document.
/// </summary>
/// <param name="inputPdfFilename">The input PDF filename.</param>
/// <param name="outputPdfFilename">The output PDF filename.</param>
/// <param name="text">A text that must be underlined.</param>
public static void UnderlineTextInPdfDocument(string inputPdfFilename, string outputPdfFilename, string text)
{
    MarkupTextInPdfDocument(inputPdfFilename, outputPdfFilename, Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationType.Underline, System.Drawing.Color.Green, text);
}

/// <summary>
/// Squiggly undeline specified text in PDF document.
/// </summary>
/// <param name="inputPdfFilename">The input PDF filename.</param>
/// <param name="outputPdfFilename">The output PDF filename.</param>
/// <param name="text">A text that must be squiggly underlined.</param>
public static void SquigglyUnderlineTextInPdfDocument(string inputPdfFilename, string outputPdfFilename, string text)
{
    MarkupTextInPdfDocument(inputPdfFilename, outputPdfFilename, Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationType.Squiggly, System.Drawing.Color.Blue, text);
}

/// <summary>
/// Markups specified text in PDF document.
/// </summary>
/// <param name="inputPdfFilename">The input PDF filename.</param>
/// <param name="outputPdfFilename">The output PDF filename.</param>
/// <param name="color">The markup annotation color.</param>
/// <param name="annotationType">The markup annotation type.</param>
/// <param name="text">A text to markup.</param>
private static void MarkupTextInPdfDocument(
    string inputPdfFilename,
    string outputPdfFilename,
    Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationType annotationType,
    System.Drawing.Color color,
    string text)
{
    // open input PDF document
    using (Vintasoft.Imaging.Pdf.PdfDocument document = new Vintasoft.Imaging.Pdf.PdfDocument(inputPdfFilename))
    {
        // for each PDF page
        foreach (Vintasoft.Imaging.Pdf.Tree.PdfPage page in document.Pages)
        {
            // extract text region of PDF page
            Vintasoft.Imaging.Text.TextRegion pageTextRegion = page.ExtractTextRegion(false);

            // search and markup all specified text on PDF page
            int index = 0;
            Vintasoft.Imaging.Text.TextRegion foundText;
            while (true)
            {
                // find next text
                foundText = pageTextRegion.FindText(text, ref index, false);
                if (foundText == null)
                    break;
                index += foundText.Symbols.Length;

                // markup found text
                MarkupText(page, foundText, annotationType, color);
            }
        }

        // save PDF document to output file
        document.SaveChanges(outputPdfFilename);
    }
}

/// <summary>
/// Markups specified text region in PDF page.
/// </summary>
/// <param name="page">The page.</param>
/// <param name="textRegion">The text region to markup.</param>
/// <param name="color">The markup annotation color.</param>
/// <param name="annotationType">The markup annotation type.</param>
private static void MarkupText(
    Vintasoft.Imaging.Pdf.Tree.PdfPage page,
    Vintasoft.Imaging.Text.TextRegion textRegion,
    Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationType annotationType,
    System.Drawing.Color color)
{
    // create markup annotation of specified type
    Vintasoft.Imaging.Pdf.Tree.Annotations.PdfTextMarkupAnnotation markupAnnotation =
        new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfTextMarkupAnnotation(page, annotationType);

    // set annotation properties
    markupAnnotation.SetArea(textRegion);
    markupAnnotation.Color = color;
    markupAnnotation.Title = System.Environment.UserName;
    markupAnnotation.CreationDate = System.DateTime.Now;

    // generate annotation appearance
    markupAnnotation.UpdateAppearance();

    // add annotation to annotations of PDF page
    if (page.Annotations == null)
        page.Annotations = new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationList(page.Document);
    page.Annotations.Add(markupAnnotation);
}