Jagged lines

Help! I can't figure out why these lines are all jagged. This is a from a past project and I'm trying to use it, but cannot figure out how to make the lines smoother. I'm wondering if I put a filter type thing on it at some point to create a vintage look with slightly uneven edges, but I can't find a setting like this anywhere. This is how the vector looks before I paste it into a new document:

I don't get it.
