Word-final sukūn is fairly rare in Classical Arabic, though it does exist in certain verb forms, pronouns and particles.
In pausal position, final short vowels are predominantly omitted. In Modern Standard Arabic, the same commonly happens also in other positions, particularly as many native speakers find it hard to apply the correct case and modus forms (which do not exist in the modern dialects). However, the sukūn sign is not normally used for this, precisely because it is optional. The text will either be fully vocalized or, if it is only partially vocalized, final letters will be left without a sign.