Once you have your recovery drive set up and have a root terminal open, go ahead and run PhotoRec by simply typing "photorec" and pressing "Enter" without any extra parameters. As always, you could preface the application with the "sudo" command to run it as root. When the program launches, you will need to select which physical disk you want to recover files from. All of your hard drives should be in this list.
Once you've selected your hard disk, you will be asked to select the partition table type. PhotoRec does this automatically for you, but you should check before hitting "Enter" just because the automator could be wrong.
Before selecting the partition table you want to recover files from on the next screen, select "File Opts" from the list to bring up the file type selection menu. Press "s" to disable all file type families and then scroll down and select the "doc" option to restrict recovery to only Microsoft Office Documents, including doc, xls, and ppt files. Press "b" to save the settings and then "Quit" back to the partition selection menu. Select your partition from the list.
Next, select the partition's file system type. This will most likely be the "ext2/ext3" option, since you are running Linux, but you may see "reiserfs" or one of the more advanced, journaling file systems that some distributions offer. This should be automatically detected by PhotoRec as well, but double check, just in case, before you hit "Enter" to continue. Next, select if you want to search the "Free", unallocated portion of the partition or if you want to search the "Whole" partition, including unerased portions.