Soldiers of the Great War (WW1) is an online searchable database for members of the CEF (Canadian Expeditionary Force)
Scanned Attestation papers (front and back) are available but it is important to realize that the Attestation papers are not the full record.
You should send for the full records of soldiers. Just provide the index entry or write to LAC with the names, dates and places of birth, parents'names and where they lived (which would hopefully be near where they signed up)
You can mail or fax your request plus your credit card number for the charges (very reasonable) I always fax as it is much quicker.
See FIND YOUR MILITARY ANCESTOR for links to the spot to request this from Library & Archives Canada