I have had this same issue and have come up with a work around. I use this method for HLR drawings of exploded views for user manuals that need to be sent to a printer for mass printing.
- Export drawing out of Solidworks as a .dwg make sure to have the high quality dwg export option checked in the options on the save as window.
- Open the .dwg file in Draftsight and select all of the entities by box selecting then change all of the line weights to 0.000". I also change the color of all entities to white so that all will be black when exported out of Draftsight.
- Export as a .pdf from Draftsight and you should have a high resolution .pdf that a print shop can work with.
It seems as though you can only get the line weight down to 0.007" in Solidworks whereas you can get much thinner lines in Draftsight or AutoCAD. Also I tried this in the newest version of Draftsight which I believe is 2015 and it did not work at all so I reloaded the older version I had which is 2014. Attached is a comparison of 2014 vs 2015 exporting of .pdf from Draftsight.
In save As option, You Can Save in PDF format from the Solidworks drawing or Part File and can take a print out of the PDF file.
if it doen't work, Check the Image Resolution in System Option.
I know this is 4 years too late, but I had this exact problem and have just solved it.
In the model view properties ensure the "Display Style" box is checked for "high quality" and NOT "draft quality"
Hope this is of use to someone.