Paulo Afonso is about 9 hours by bus from Salvador (about R$70).
The main attraction is the Paulo Afonso Hydroelectrix Complex, which contains three dams and provides power for much of Northeast Brazil. Visitors can take a tour of the complex for R$25 per person (plus R$30 per group if you don't have your own car). Inquire at the tourist information center on Av. Apolônio Sales.
Prainha is a beach on a reservoir created by one of the dams. A nice place to relax. There are several restaurants here.