how to read text from pdf file in C#

public  string GetPDFText(String pdfPath)
    {
        PdfReader reader = new PdfReader(pdfPath);

        StringWriter output = new StringWriter();
        String _text = String.Empty;
        int _subpage = 0;
        Int16 PerPageText = 2000;//char
        Int32 PageNumber = 1;

        for (int i = 1; i <= reader.NumberOfPages; i++)
        {
            _text = _text+PdfTextExtractor.GetTextFromPage(reader, i, new SimpleTextExtractionStrategy());
            _subpage = (_text.Length - _text.Length % PerPageText) / PerPageText;

            if (_subpage > 0)
            {
                for (int j = 0; j < _subpage; j++)
                {

                    output.WriteLine("Page " + PageNumber.ToString() + "<br />" + _text.Substring(PerPageText * j, PerPageText) + "<br /><br />");
                    PageNumber = PageNumber+1;
                }
                _text = _text.Substring(_text.Length - _text.Length % PerPageText, _text.Length % PerPageText);
            }
            //else {
            //    output.WriteLine("Page " + i.ToString() + "<br />" + _text+ "<br /><br />");
            //}
            
        }

        return output.ToString();
    }