[Sorry chrism01, above, our posts crossed. I didn't see yours before I posted mine below]
She means go to a shell prompt using a terminal window (where you normally type commands etc, with the $ prompt), and then type the command:
... which, if they were regular text files would display the file contents in plain text ... but, given that .doc and .pdf are binary files I'm not sure how helpful that will prove.
You could also accomplish the same thing using the "less" command, or the "more" command, instead of using "cat."