We frequently print off some mockups on plotter paper with the provided Pen that came with our cutter. The pen would frequently go out, and looking at designs from a distance, you couldn't see the lines very well.
One day, I was tracing the pen lines with a sharpie and thunk...why not just put the sharpie in the cutter? Works like a charm!! Had to take some masking tape and wrap a few layers around the base of the pen, but it makes things much easier.