If you haven’t paid RPRF fees in the beginning, then as per my knowledge ADVO is discouraging to pay it until they requested.rtamimi said:Dear Lemans,
I live now in Saudi Arabia,Riyadh.
I paid RPRF after a month of the medical exam, they did not ask me to pay.
But I paid to avoid the delay it will take when they send PPR,I think you can pay it anytime during the application process.
Refer: http://www.canadainternational.gc.ca/uae-eau/visas/fees-frais.aspx
On a side note, if you haven’t paid RPRF then don’t worry, they will request later (may be with Passport request etc.)