* CFO Penido to step down Friday after 9 months
* Chief Executive Frederico Curado taking interim role
SAO PAULO, April 12 (Reuters) - Brazil's Embraer, the world's third-largest commercial planemaker, said on Thursday that Chief Financial Officer Paulo Penido Marques has resigned, forcing the company to fill that post for the second time in a year.
Penido, who had been Embraer's CFO for nine months, will step down on Friday to "take on new professional challenges," Embraer said in a securities filing.
Chief Executive Frederico Curado will expand his duties to include interim chief financial officer during the search for a new CFO, which has reached "an advanced stage," Embraer said.
Penido joined Embraer in July 2011, when he replaced Cynthia Marcondes Benedetto, who served as chief financial officer from January 2011.
Penido had previously served as CFO of Brazilian steelmaker CSN. He was named recently to serve on the board of steelmaker Usiminas beginning April 25.
Embraer shares were up 0.6 percent in Sao Paulo trading to 15.92 reais after the announcement, less than the 1.8 percent advance of the benchmark Bovespa stock index.