There are variables
First is the going to be the Market area, then the size of the company, and how many printers are you running and what type and what sort of work are you actually expected to do? Each company is going to be slightly different. If you believe you are underpayed then you need to take it up with the Owner of the Company or your direct manager. When looking at an increase in pay, there are many things the owner is going to look at it. One are you worth the pay? Meaning the work you do, do you return double or triple that in income? Can and will somebody do it for less? Your years in service, and how knowledgable you are in general not only about your particular job, but the rest of the company. Meaning how versatile are you? Are you dependable, meaning are you ALWAYS ontime, how many sick days do you take, what is your work ethic?
In my area, print operators are not Skilled and therefor are typically Minimum wage earners. Depending on what their Job duties actually include.