If you move to a battlefield twice, does Pendulum Blade stack twice in one round Riftbound?

Yes, Pendulum Blade's triggered ability stacks if the equipped unit moves to a battlefield twice in one turn.

Each time the equipped unit moves to a battlefield, Pendulum Blade's trigger fires separately — "When I move to a battlefield, give me +2 Shield this turn" has no "once per turn" restriction. Both instances of "give me +2 Shield this turn" are active simultaneously, and Rule 814.2 states that Shield values from different sources sum together. So two moves = +4 Shield total for the turn.

The only practical hurdle is finding ways to move the same unit to a battlefield twice in one turn — effects like Ride the Wind, Zenith Blade, or a combination of Standard Move + a movement spell can do it.