Playstation 3 is a console which is able to run games from a Blue-ray or a DVD disc and the peripherals that are available (keyboard, mouse, microphone, motion devices) are only used for gaming purposes. Although the latest version of the firmware has Facebook, Youtube or any other social application, the keyboard can only be used to type into these applications only. Plus there are no applications available for writing using the Playstation 3 console so the answer to this question would be no, you can’t write or open documents on the Playstation 3.
