1. RPRF Fee can be paid online by credit / debit card (I Paid using my ICICI Debit Card). Refer below link:
http://www.cic.gc.ca/english/infORmation/fees/index.asp
The fee is CAD 490 or INR 24,200 per Adult. There is no fee for child under 18. Else you can send of equivalent amount of DD payable at New Delhi, if your visa office is New Delhi.
2. All the docs (Medical Receipts, PCC, DD/RPRF Fee receipts, Passport bio pages etc.) are required to be sent to your Visa Office. Please read the letter which you have recd. for your Medicals. It states "Please mention our complete file no. on you correspondence and address your correspondence to High Commission at the address indicated below" ------- Check what is the addres mentioned below. If your VO is NDVO, then the address will be:
Immigration Section,
7/8, Shantipath, Chanakyapuri, New Delhi - 110021, India
If any other address, then send it to that address....
Best of Luck...