How do i convert a pdf to an autocad file (dwg) in illustrator?

the file is a pdf, but it's not a vector image so i'm guessing that is why it is not importing properly. i also tried live trace on illustrator but there were WAY too many lines when i imported it into cad. the file is a deck plan of a cruise ship so it's pretty detailed & tracing it with the pen tool might be a lil difficult. if anyone has any other options i can try or can give me a step by step thing on what to do, it would be greatly appreciated! (: