99% of the time, no, they aren't going to peek through your documents, they could care less, unless they notice something suspicious while doing what ever on the machine.
A very small amount of people, a technician isn't going to spend an hour on a machine trying to find something that doesn't exist in most cases, especially if they are having to deal with hardware. Have worked at enough shops in my time that technicians can get in some trouble with the boss because it's cutting into profits, unless as I said, the technician noticed something suspicious.