When wearing a suit, does the suit jacket pattern have to fit the pants?

From a distance the two will blend together, so no worries! They are both black and that's' what's important. Today's fashion is all about mixing rather than matching so by mixing a plain and a subtle pattern (which "reads" as a neutral) you are following current trends and that combo sound fine. Just be sure to add something bright or metallic to the mix, or maybe a few bursts of bright red accessories; very elegant and chic.