Here scribe 2 of 𝓞 immediately corrected to to unto, but when copying from 𝓞 into 𝓟, Oliver Cowdery ignored the inserted un before the to. Elsewhere in the Book of Mormon text, in the context of “pertaining righteousness”, to occurs five times and unto four times. So either reading is possible in 1 Nephi 15:33. Perhaps the to in the preceding phrase (“as to things which are spiritual”) led scribe 2 and Oliver to write down to in “pertaining to righteousness”. Scribe 2’s correction of his initial to to unto apparently represents his attempt to get Joseph Smith’s dictation down as accurately as possible.
Summary: Restore the preposition unto in 1 Nephi 15:33 (“which are pertaining unto righteousness”).