Convert PDF Documents to TXT Documents
val cPDFConvert = CPDFConverterTxt(context, uri, "")
val params = CPDFConvertTxtOptions()
val result: ConvertError = cPDFConvert.convert(outputDir, outputfilename, params, pageArrays,
onHandle = onHandleCal,
onProgress = onProgressCal,
onPost = onPostCal)