You can use pronouns to avoid unnecessary repetition of nouns, but bear in mind that pronouns are effective only when they are used to avoid unnecessary repetition. They can become a source of confusion if you use a pronoun when repeating a noun is necessary to make the meaning clear.
Consider the following example:
The author has written a biography of Mark Twain that reveals his great sense of humor.
Readers are likely to wonder whose great sense of humor is revealed. Does the writer mean the sense of humor of the author or of Mark Twain?
The problem is the pronoun his. Its antecedent could be the author or Mark Twain. Its reference is ambiguous. To remove the ambiguity, revise the sentence so that it states the meaning directly. The most direct way is usually to repeat the necessary noun.
The author has written a biography of Mark Twain that reveals Twains great sense of humor.
How can you remove the ambiguity of an ambiguous pronoun?