Everybody stand back! :)
As was well stated, someone has already written things to get text out of PDFs for you. The second problem of finding sentences with "Asia" in them is more interesting, and should be a good learning exercise for you.
So, pretending that you already have a plain text file full of, erm, text available, how would you go about identifying asian sentences in it? Do you have an idea how you would begin? (Trying to ascertain what you already know/what you have already written)
I'm a peripheral visionary... I can see into the future, but just way off to the side.