this was really useful in a pinch since i was stuck at rutland, vt station which has no ticket window to validate an evoucher from a family member (and the phone operator similarly could not do so without verification).
the online system only required the other passenger's email or AGR and thus was pretty seamless, even on a handheld using the regular browser. after adding/verifying the numbers, just don't forget to still tick the box to include the evouchers if redeeming several.
(luckily there was just enough dusk on sunday's SB to the see the VT leg until whitehall, ny, where i was already acquainted with the adirondack line)