please help me in this regard

It depends if you are using Pro/Toolkit or Object Toolkit.

For Pro/Toolkit you should use ProPDFExport API. For Object Toolkit have a look at pfcPDFExportInstructions and pfcPDFOptions classes.

If you are using C / C ++ TOOLKIT
You can find the C / C ++ TOOLKIT example code in article CS61272.

https://www.ptc.com/ko/support/article?n=CS61272&language=en&posno=5&q=toolkit%20export%20pdf&source=search