A 'pro se' divorce is an uncontested divorce; a divorce where both parties agree on everything and there are no disputes over custody of children, division of property/assets/debt, alimony, child support, etc. If this applies to your situation, you only need proper divorce paperwork to end the marriage.
If you already have prepared your divorce forms and signed them, you do not need a lawyer to file your papers with the state. That said, there are people who hire an experienced lawyer in their area to carefully review and amend their documents prior to submitting them to the court. This is what is known as a ‘hybrid’ online uncontested divorce.
If you were to pursue this route, you would pay a lawyer for the time it takes them to review and modify (if necessary) your divorce papers. Depending on the lawyer you hire, you could spend anywhere from $250-$500 per hour (possibly more in major metropolitan areas).