''' <summary>
''' Removes all bookmarks of PDF document.
''' </summary>
''' <param name="pdfFilename">The filename of PDF document.</param>
Public Shared Sub RemoveAllBookmarks(pdfFilename As String)
    ' open PDF document
    Using document As New Vintasoft.Imaging.Pdf.PdfDocument(pdfFilename)
        ' get the collection of bookmark of PDF document
        Dim bookmarks As Vintasoft.Imaging.Pdf.Tree.PdfBookmarkCollection = document.Bookmarks

        ' if PDF document has bookmarks
        If bookmarks IsNot Nothing Then
            ' clear bookmarks of PDF document
            bookmarks.Clear()
        End If

        ' save changes to a file
        document.SaveChanges()
    End Using
End Sub

/// <summary>
/// Removes all bookmarks of PDF document.
/// </summary>
/// <param name="pdfFilename">The filename of PDF document.</param>
public static void RemoveAllBookmarks(string pdfFilename)
{
    // open PDF document
    using (Vintasoft.Imaging.Pdf.PdfDocument document = 
        new Vintasoft.Imaging.Pdf.PdfDocument(pdfFilename))
    {
        // get the collection of bookmark of PDF document
        Vintasoft.Imaging.Pdf.Tree.PdfBookmarkCollection bookmarks = document.Bookmarks;

        // if PDF document has bookmarks
        if (bookmarks != null)
            // clear bookmarks of PDF document
            bookmarks.Clear();

        // save changes to a file
        document.SaveChanges();
    }
}