Voucher can be used for booking flights and hotels through Air Canada website. Here is the briefing from Air Canada about the voucher
"We are happy to send you an Air Canada Travel Voucher with a value of 617.11 USD. The voucher is fully transferable, can be used multiple times and will never expire.
For your protection, a separate email will be sent with the four-digit pin code needed to book a flight or associated service online at www.aircanada.com, or when you call Air Canada Reservations at 1-888-247-2262 (for international and other numbers, visit www.aircanada.com/othernumbers). If you would like to book an Air Canada flight with your travel agent, please contact them directly.
You can also use your voucher to book a flight and hotel package to Mexico and the Caribbean only (excluding group reservations.) Visit www.aircanadavacations.com to book."