How do I know if I'm being exploited at work as opposed to being given more opportunities to grow? I know there are two sides to every coin, but there has to be a line right?

Seeing your portfolio expand is a good thing as it can justify your contribution in your appraisal. The question is then whether do you see a mismatch in the expected reward that you are getting.

Hello! Being exploitated are things like doing filing work or menial tasks. If you're being utilized too much for that, perhaps you can voice out to your superior.

sometimes superior needs to be communicated so they know you are unhappy about it!