HOW TO: Extract and Redact Text from a File Based on a Regular Expression

            string inputFile = @"C:\Users\Public\Documents\LEADTOOLS Images\leadtools.pdf";
            string outputFile = $@"{Path.GetDirectoryName(inputFile)}\{Path.GetFileNameWithoutExtension(inputFile)}-redacted.pdf";
            using (var ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.LEAD, false))
            {
               ocrEngine.Startup(null, null, null, OcrEnginePath);
               var options = new LoadDocumentOptions();
               using (var document = DocumentFactory.LoadFromFile(inputFile, options))
               {
                  document.IsReadOnly = false;
                  document.Text.OcrEngine = ocrEngine;

                  RasterImage redactedDocument = document.Pages.First().GetImage();
                  foreach(var page in document.Pages)
                  {
                     if (page.PageNumber == 1)
                        continue;
                     redactedDocument.AddPage(page.GetImage());
                  }

                  Parallel.ForEach(document.Pages, (page) =>
                  {
                     AnnContainer container = new AnnContainer();
                     var pageText = page.GetText();
                     pageText.BuildWords();

                     //Regex to search for all instances of LEADTOOLS or LEAD
                     var pattern = "(LEADTOOLS|LEAD)";
                     var rgx = new Regex(pattern, RegexOptions.IgnoreCase);
                     var annotations = new ConcurrentBag<AnnRedactionObject>();
                     Parallel.ForEach(pageText.Words, (word) =>
                     {
                        if (rgx.Match(word.Value.ToLower()).Success)
                        {
                           AnnRedactionObject redactionObject = new AnnRedactionObject();
                           redactionObject.Rect = word.Bounds;
                           redactionObject.Fill = AnnSolidColorBrush.Create("Black");
                           annotations.Add(redactionObject);
                        }
                     });

                     var imagePage = page.GetImage();
                     foreach (var annotation in annotations)
                        container.Children.Add(annotation);

                     AnnWinFormsRenderingEngine e = new AnnWinFormsRenderingEngine();
                     e.RenderOnImage(container, imagePage);

                     redactedDocument.ReplacePage(page.PageNumber, imagePage);
                  });

                  using (RasterCodecs codecs = new RasterCodecs())
                     codecs.Save(redactedDocument, outputFile, RasterImageFormat.RasPdfJpeg, 0);

                  redactedDocument.Dispose();
                  Console.WriteLine($"File has been successfully redacted, and saved to {outputFile}");
               }
            }