The lift pass kiosks are open until 16:30 but you're usually ok until 16:45. You can pre-book them on the online shop here and you'll save money if you're booking ski/snowboard hire at the same time.
I'm travelling out on Sunday 24th Feb for a week. I haven't bought my lift pass yet and am trying to decide whether to get it in advance or just buy in resort. Based on a 10.35 arrival time at Lleida airport I'm guessing I'll get to Pas by 2-3pm and need to know if this will give me time to get my pass on Sunday afternoon or whether I'm better prebooking it with Neilson?