The Percy Jackson series by Rick Riordan has been a beloved favorite among young readers and fantasy enthusiasts alike. The series follows the adventures of Percy Jackson, a young boy who discovers he is the modern-day son of the Greek god Poseidon. The fifth book in the series, "The Last Olympian", was published in 2009. However, it seems that there is a PDF version of the book available on Google Drive, specifically titled "El Expediente del Semidios" (The Demigod Files) which is a companion book to the series.