It depends on the location of the PPR recipient. If he (assuming a male) is in a location where there's a VAC office near (within the same city or country), then he will need to use that VAC and they will deliver to Nairobi Canada consulate.
If not, then he needs to use courier service like DHL to send the documents directly to Nairobi VAC and they will send to Canada consulate in Nairobi; for this scenario, contact Nairobi VAC to guide him on the procedure as Nairobi VAC will require DHL consent form and return label to be added in the list of documents to be sent.
In fact, the best is to contact Nairobi VAC and inform them your location and that you need passport transmission service as you (the applicant) received PPR from Canada.