Pronominalization is appropriate when the noun in an embedded clause (a constituent part of another clause) is identical to the noun in the matrix clause (which contains the embedded clause). In referring to the noun in the matrix clause, pronominalization is often used. Look at these examples where the noun in the matrix clauses (bolded) is replaced by the pronoun it in the embedded clauses (italicized):
SUMMARY/OBSERVATIONS: When pronominalization is used in an embedded clause, the pronoun is usually omitted. Notice also that each of the verb preceding the pronoun is always transitive.