def convert()
      errors = ""
      output = ""
      
      if @user_pwd 
        cmd = "pdftohtml -stdout #{@format} -upw #{@user_pwd}" + ' "' + @path + '"'    
      elsif @owner_pwd 
        cmd = "pdftohtml -stdout #{@format} -opw #{@owner_pwd}" + ' "' + @path + '"'
      else
        cmd = "pdftohtml -stdout #{@format}" + ' "' + @path + '"'
      end
      
      output = `#{cmd} 2>&1`

      if (output.include?("Error: May not be a PDF file"))
        raise PDFToHTMLRError, "Error: May not be a PDF file (continuing anyway)"
      elsif (output.include?("Error:"))
        raise PDFToHTMLRError, output.split("\n").first.to_s.chomp
      else
        return output
      end
    end
def convert()
      errors = ""
      output = ""
      
      if @user_pwd 
        cmd = "pdftohtml -stdout #{@format} -upw #{@user_pwd}" + ' "' + @path + '"'    
      elsif @owner_pwd 
        cmd = "pdftohtml -stdout #{@format} -opw #{@owner_pwd}" + ' "' + @path + '"'
      else
        cmd = "pdftohtml -stdout #{@format}" + ' "' + @path + '"'
      end
      
      output = `#{cmd} 2>&1`

      if (output.include?("Error: May not be a PDF file"))
        raise PDFToHTMLRError, "Error: May not be a PDF file (continuing anyway)"
      elsif (output.include?("Error:"))
        raise PDFToHTMLRError, output.split("\n").first.to_s.chomp
      else
        return output
      end
    end
Convert the PDF document to HTML.  Returns a string