Mysterious line on pdf
Mysterious line only shows in pdf. It's not visible in model space nor paper space-all layers on. What's causing it?
A ghost line
I would use list command and try to identify the entity.
It may be a line that is the same color as your screen background or some other color that is invisible onscreen.
You could use delete command to see if it exists and erase it.
If you have tried all the usual stuff, I would run AUDIT on the drawing file. Chances are it will find and fix an error or two.
If that does not work, -PURGE would be my next move.
Try a different print driver. I usually use dwgtopdf to good effect.
Turn off all the layers in the drawing and then generate another pdf. If the line still shows up there's a good chance it's the print driver. The only other "might be" I can think of is to slam the dwg flat with no 3d and see if it still shows up. Can't help but think paper space is the culprit although you've tried it in model space also.