I would assume from the title of the pattern that it's not connected for in-the-round knitting. "Jacket" almost always means cardigan/buttoned/zippered style.
* Is there a photo or drawing of the jacket? If it's open at the front, or buttoned or zippered, then it's not going to be in the round.
* In the directions, do they say at any point, "join"? If they don't, then it's knit flat.
* Do the instructions use the terms rows, or rounds, as Suzeeq described? Rows are for flat, rounds are for tubes.