last i checked, PDAs are just a quality of life thing that's adopted by a lot of communities to save time, at least in terms of messaging other players. otherwise it's a small computer that can be used to read books, draw sketches, play music, watch shit etc. it can also interface with the bigger computers including fednet terminals. i'm pretty sure the criminal databse the marines can access pertains to the current ship which isn't that big piece of information, same for medical records. discs are mail, as illustrated in the movie when rico gets a message from carmen.
bits and pieces for communication