When a drafting document contains very large but also very small elements, it potentially reaches the limit of the resolution of the printer you are using and this is even more true when printing in PDF.
This causes aliasing on these small curves.

To avoid this, you have to increase the resolution of the printing by launching the File > Page setup function and choosing the Configuration button .
Then in the printer configuration window, check the Dot per inch option and enter the value (300 or 600).