Smooth line art problem

[Drew5F9B]

I need to plot CAD site plans to PDFs and whenever I do some lines on the drawing show up much lighter than others, seemingly at random as many of these lines are from the same layer in CAD. The lineweight problem can be solved when unchecking the smooth line art box in preferences but the lines are, obvioiusly, not smooth. They are chunky and difficult to see detail. How can I find the happy medium of smooth line art that doesnt have varying lineweight?

[OYSTEIN0101]

Did you ever figure out a good solution? 
Either on the cad plot to pdf side, or the acrobat viewing side? 

[Eric Dumas]

Hi,

• Can you confirm the name and version of the software you are using?
• In AutoDesk AutoCAD, there are 2 main ways to make a PDF
  • Export to PDF
  • Plot command, I prefer this one, as it uses the old but trusted pen assignment, which matches the layers' colours.

[OYSTEIN0101]

Autocad LT 2019. 
Using Plot command and AutoCAD PDF (HQ print or General). printer

[Tariq Ahmad Dar]

Hi 

Thanks for reaching out with your question. 

Following are some suggestions:

Modify Adobe Acrobat Rendering

• Keep “Smooth Line Art” enabled but also enable Enhance Thin Lines under Preferences → Page Display to balance the visibility.
• If needed, disable “Use Overprint Preview” in Acrobat (sometimes it affects vector rendering).

Flatten the PDF for Consistency (if you have access to the Illustrator app)

• Open the PDF in Adobe Illustrator or another vector editor.
• Convert vector lines into high-resolution raster (e.g., 1200 DPI).
• Save as a new PDF with preserved lineweights.

Here is something I found a few users discussing a similar behavior(not tested personally):

Adjust the CAD Export Settings

• When exporting to PDF from AutoCAD, use the DWG to PDF.pc3 plotter instead of the default PDF export.
• In the Plot settings, ensure:
• Line merge is enabled (Prevents overlapping lines from being lightened).
• Use TrueType fonts instead of SHX fonts (SHX can cause artifacts).
• Set high DPI (e.g., 600-1200 DPI) for better rendering.
• Use monochrome.ctb or adjust pen assignments to ensure consistent lineweights.

~Tariq

[OYSTEIN0101]

Disabling 'Smooth Line Art' is the only thing that kind of gives an ok result. If enabled it looks like this:  

I have tried all your other suggestions in Acad and Acrobat, except the fonts. But I struggle with lines as well, not only fonts, so changing font type would not fix the lines. 
The only thing that seems to help is to use an older Acrobat reader or another viewer (even Edge and Chrome).  So my conclusion is that it is an Acrobat display error. 
The pdfs I'm struggling with are created in A0 size, and from zoom level 400% on a fullHD screen the problem is no longer visible.