You're welcome. And no, other than zooming in closely, I don't know of a different way. The zooming in is pretty clear to me (even with my bad, old eyeballs). A raster will get pixelated pretty quickly by, say, 400%.
I think another way would be to insert that pdf into another new drawing, and if it is a vector, the linework and other entities will be individually selectable in cad, whereas with a raster it will be one monolithic image, just as a .jpg or .bmp is when inserted into cad.
Jeffrey Rivers
Win 10 Pro 64-bit, Intel i9 3.7GHz, 64 GB
NVIDIA RTX A4000
C3D 2020 V13.2.89.0