What happens if you play Barrage and you don’t have enough cards…?

If you don’t have enough cards to pass one to each other player then you end up drawing.
You draw 2 at a time and give a card to each remaining player.

Example
In a four player game (you and three others) if you play Barrage and you only have one other card in your hand you would pass that card to a player.
Then draw 2 pass each of those cards to the remaining two players and draw 2 more cards since you are now out.