Here’s a screen shot from the PDF scaled up to 500%.
Increasing the lineweight above two tenths of a pixel wide helps, too. I set it to 0.5 for the above.
You can set Display Resolution to High in Document Setup>Paper and that will improve the resolution while you are working but it tends to make your graphics card work much harder which slows things down.
By the way, it wouldn’t hurt to purge unused stuff from your SketchUp model once in awhile. I purged the .skp file in your LO file and got rid of this.
Reduced the LayOut file size by nearly 53%.
Also it would be wise to set up a scene for the view in SketchUp and use that for the viewport instead of the Last saved SketchUp view. Using Last saved Sketchup view opens you up to all kinds of trouble.