Free options for Swiss pairing include www.swips.eu
(it's free for 'small' tourneys only, I'm not sure how many players maximum), www.rrweb.org/javafo/JaVaFo.htm
(totally freeware), www.vegachess.com
(it's just a GUI for the same JaVaFo; the Linux version is totally freeware, the Windows one is free up to 30-player tourneys only), http://oswiss.ryuu.eu/
(free, under the BSD licence). I haven't tested either of them. Don't believe that 'aoslm' spammer who upvotes SWIPS and downvotes other pairing software at all comparison websites.
the big problem is that your requirement 'no one plays anyone from the same pack' (not even in the second or further rounds) is so non-standard that the usual Swiss tourney software is likely unfit for satisfying it because there's hardly ever such a requirement in serious tournaments.