I have never used Plot so I can't comment on that.
But when you print you will have options for the Printer Setup.
In there you should find settings that control the quality of the print.
These may be set to a low or draft quality by default.
One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10