In these sentences, are him and her the direct objects? If so, should they be translated as lo and la? I know him: Le conozco / Lo conozco I know her: Le conozco / La conozco When is le acceptable?
What Julian refers to is called "Leismo."
Leísmo ("using le") is a dialectal variation in the Spanish language that occurs largely in Spain. It involves using the indirect object pronoun le in place of the (standard) masculine direct object pronoun lo, especially when the direct object refers to a male person.
Leísmo with animate objects is both common and prescriptively accepted in many dialects spoken in Spain, but uncommon in most others. Leísmo is always rejected in Linguistic prescription when the direct object to which it refers is not an animate object.
You can see some examples here at this link.
Julian, can you explain? I have only seen that Lo and La are the direct object pronouns, whereas Le would be the indirect object pronoun used in a different situation (to/for him).
Le conozco = I know him. (Sometimes Lo is used, but Le is more proper).
La conozco = I know her. (La always).