using SautinSoft.Pdf;
using (var document = new PdfDocument())
  {
   var page = document.Pages.Add();
   var formattedText = new PdfFormattedText();
   formattedText.FontSize = 15;
   formattedText.FontFamily = new PdfFontFamily("Calibri");
   formattedText.Color = PdfColor.FromRgb(1, 0, 0);
   formattedText.Append("Hello World!");
   page.Content.DrawText(formattedText, new PdfPoint(110, 650));
   document.Save("Hello World.pdf");
  }

using (PdfDocument document = PdfDocument.Load("Find.pdf"))
 {
     foreach (var page in document.Pages)
     {
         var search = page.Content.GetText().Find("North");
         foreach (var text in search)
         {
             var element = text.Elements.First();
             var font = element.Format.Text.Font;
             double size = Math.Min(text.Bounds.Height, font.Size * element.TextTransform.M11);

             using (var formattedText = new PdfFormattedText() { Font = font, Color = PdfColor.FromRgb(1, 0, 0), FontSize = size })
             {
                 formattedText.Append("South");
                 page.Content.DrawText(formattedText, new PdfPoint(text.Bounds.Left, text.Bounds.Bottom));
             }
             text.Redact();
         }
     }
     document.Save("Replace.pdf");
 }

using SautinSoft.Pdf;
using (PdfDocument document = PdfDocument.Load(@"Input.pdf"))
 {
   // Assume we want to redact (delete) the word "the"
      string textToRedact = "the";
      foreach (var page in document.Pages)
      {
         var texts = page.Content.GetText().Find(textToRedact);
         foreach (var text in texts)
         {
            text.Redact();
            // Draw a green rectangle instead of removed text.
            var bounds = text.Bounds;
            var rectangle = page.Content.Elements.AddPath().AddRectangle(new PdfPoint(bounds.Left, bounds.Bottom), new PdfSize(bounds.Width, bounds.Height));
               rectangle.Format.Fill.IsApplied = true;
               rectangle.Format.Fill.Color = PdfColor.FromRgb(0, 1, 0);
               }
            }
           document.Save(@"Redacted.pdf");
          }

using SautinSoft.Pdf;
using (var document = PdfDocument.Load(pdfFile))
   // Group fields by name because all fields with the same name are actually different representations (widget annotations) of the same field.
   // Radio button fields are usually grouped. Other field types are rarely grouped.
   foreach (var fieldGroup in document.Form.Fields.GroupBy(field => field.Name))
   {
      var field = fieldGroup.First();
      fieldType = field.FieldType;
      fieldName = '"' + field.Name + '"';
      fieldValue = field.Value;
      foreach (var widgetField in fieldGroup)
        {
         switch (widgetField.FieldType)
         {
           case PdfFieldType.CheckBox:
           case PdfFieldType.RadioButton:
              // Check box and radio button are toggle button fields.
              var toggleField = (PdfToggleButtonField)widgetField;
              fieldExportValueOrChoice = toggleField.FieldType == PdfFieldType.CheckBox ?
                    writer.WriteLine(separator);
                }
            Console.Write(writer.ToString());
        }