With the 1000A, you just move to where you want the new origin to be, and press 'origin' & enter or function, (I'm going from memory).
It is simple.
If using corel, it'll stop wherever it finishes-then pressing origin takes you back to the original starting point, but you can reset the origin via the keypad. It is straightforward- just play with it & try the options.
Don't forget to reset it later, back to normal though.
If it's the pnc 1000, I've not done it- never bothered with that. It was easier to turn it off & turn it on again, and do a new plot, setting up what you want in the driver/print preview.
I never did work out how to override the default 5 ft length though, (with corel) so always broke the plots into whatever was a convenient length, just a bit shorter than that.