In the original text for this verse, the indefinite article a is repeated in the phrase “a king and a ruler”. In the 1840 edition, the repeated a was omitted, probably accidentally. The RLDS text restored the repeated a in the 1908 edition. The tendency to drop the repeated a is fairly common in the history of the text. For another example involving “a king and a ruler”, see 1 Nephi 16:38. For a complete discussion, see under conjunctive repetition in volume 3.
Here in Jacob 1:9, the first a in this conjunctive expression was accidentally omitted in three early 20th-century LDS editions (1902, 1905, and 1911). The 1920 LDS edition restored this first a. The phraseology “to be king and a ruler over his people” is not impossible since elsewhere in the text there are instances of “to be king” (that is, without any article):
Besides here in Jacob 1:9, there are other instances of “to be a king”:
More significant for analyzing Jacob 1:9 is the fact that whenever king is conjoined with a semantically related conjunct like ruler, leader, or protector, there is always a determiner (almost always a) for both conjuncts:
Thus the secondary readings “to be a king and ruler” and “to be king and a ruler” in Jacob 1:9 are inconsistent with all other usage in the text.
Summary: Maintain the repeated determiner in Jacob 1:9: “he anointed a man to be a king and a ruler”.