The way Criterion is able to take an old movie and release high definition transfers is because they have the original film. They load the film in to a special scanner that does really high resolution scans of each frame that are then cleaned up by hand and with specialty programs.
But hey, taking a VHS tape of Unknown Creature, transferring it to DVD, ripping the DVD, and then increasing the resolution of the rip with premiere is basically the same thing and will get as good, or even better, results than the team at Criterion.