iTextSharp how to add Cyrillic font in PDF document

I have a previously created PDF file. I want to add a stamp to it with Cyrillic characters and a frame. For example

For this i use iTextSharp 5.5.13.3 I can make a rectangle, but when I want to add text, I get an error:

System.ArgumentException: 'windows-1252' is not a supported encoding name. For information on defining a custom encoding, see the documentation for the Encoding.RegisterProvider method. (Parameter 'name')

Code that does this:

                    PdfTemplate layer2 = appearance.GetLayer(2);
                    String text = " Копия ВЕРНА\n"
                                  + " Дата: " + DateTime.Now.ToString("dd.MM.yyyy HH:mm") +"\n";
                    string externalFont = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Fonts), "Arial.TTF");
                    BaseFont externalBaseFont = BaseFont.CreateFont(externalFont, BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED); **Throws an exception here!** 
                    Font font = new Font(externalBaseFont,6, Font.NORMAL, BaseColor.BLACK);
                    float size = font.Size;
                    float margin = 1;
                    Rectangle dataRect = new Rectangle(margin, margin, appearance.Rect.Width- margin, appearance.Rect.Height - margin);
                    if (size <= 0)
                    {
                        Rectangle sr = new Rectangle(dataRect.Width, dataRect.Height);
                        size = ColumnText.FitText(font, text, sr, 10, appearance.RunDirection);
                    }
                    ColumnText ct = new ColumnText(layer2);
                    ct.RunDirection=(appearance.RunDirection);
                    ct.SetSimpleColumn(new Phrase(text, font), dataRect.Left, dataRect.Bottom, dataRect.Right, dataRect.Top, size, Element.ALIGN_LEFT);
                    ct.Go();
                    layer2.SetRGBColorStroke(0, 0, 0);
                    layer2.SetLineWidth(0.5);
                    layer2.Rectangle(dataRect.Left, dataRect.Bottom, dataRect.Width, dataRect.Height);
                    layer2.Stroke();