Convert PDF to text file with whitespace is represent as comma(,)

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C#3.5

C#5.0

StringBuilder text = new StringBuilder();
            PdfReader pdfReader = new PdfReader(pdfFile);
            for (int page = 1; page <= pdfReader.NumberOfPages; page++)
            {
                ITextExtractionStrategy strategy = new SimpleTextExtractionStrategy();
                string currentText = PdfTextExtractor.GetTextFromPage(pdfReader, page, strategy);
                text.Append(System.Environment.NewLine);
                text.Append("\n Page Number:" + page);
                text.Append(System.Environment.NewLine);
                currentText = Encoding.UTF8.GetString(ASCIIEncoding.Convert(Encoding.Default, Encoding.UTF8, Encoding.Default.GetBytes(currentText)));
                text.Append(currentText);
                pdfReader.Close();
 

            }
            richTextBox1.Text += text.ToString();

I use this code but it comes continually one after sentence i want to represent the continue two whitespaces can represent as comma(,) plz help some one