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Hi @Anonymous 

Please specify AutoCAD version you are using.

I think the problem is that you are using extremely small scale for PFD output and PDF printer doesn't have enough resolution to create such small objects.

If you are using AutoCAD 2019 or above, you may try to use AutoCAD (Hight Quality Print).pc3 printer and even adjust its settings and increase Vector quality to 4800 dpi or greater: