We learn that Frank Heffley, Greg's father, works in an office, but beyond that, we don't know what his specific job is or the name of his company. At least one illustration shows him seated and working at a computer, which suggests he is a white collar employee. We also learn that it is important to him that his children make a good impression on his boss, which shows he both cares about his job and about how his family appears to the people he works with. Frank also seems to be a hard worker.
Mostly, however, we see Frank at home, where he wants his kids to be strong, self-sufficient, and do things right. For example, he gets upset at Rodrick's mistakes when typing. It seems that Frank, a caring if sometimes overwrought dad, wants his sons ultimately to be able to be successful on a job.