You do not need to get copies of these certified unless you are getting them translated. if they are already in english then copies do not need to be certified. Unless they are specifically asking you to certify them in the additional doc request.
see:
http://www.cic.gc.ca/english/information/applications/guides/5289ETOC.asp
Under Step 2. Gather Your Documents
Make sure all photocopies are clear and easy to read. Other than copies of original documents used for translations, photocopies
do not need to be certified. Don’t send originals unless we ask for them, because they
will not be returned.