Yes - You can purchase the AP vouchers online, over the phone, in a
Disney Store, etc. and link them to your
MDE account. You will not be able to make any FP+ reservations prior to your travel unless you have purchased the vouchers ahead of time. If cash flow allows it, I would recommend purchasing your AP's now. From a FP+ perspective, there's no real advantage to buying any further out than 60 days prior to your travel, as this is the earliest that you can begin to make your reservations, but I would do it anyways to avoid any potential ticket price increases between now and then.
Once you arrive at the front gate of your first park, you will need to visit Guest Relations in order to activate the AP's.