I have noticed recently that the line weights in my drawings are acting strange. Everything
seems and appears fine within AutoCAD, but as soon as I plot to PDF or
plot direct to printer, the line weights mess up and some are thicker
then others! There doesn't seem to be any pattern to certain lines that
mess up, it appears to be fairly random. This is really starting
to annoy my now because I have a shed load of P&ID's that need
amending with line weights that need to vary in thickness etc, and I
simply can't complete the work while this is happening!I have
attached the original DWG file.
If anyone can take a look and let me know if they have the same issue at their end OR shed some light on this and help me sort things out, that
would be fantastic! uploads/11333/C-PRO-PFD-320-00002_Option_2.dwg

P.S. I have tried updating my graphics drivers etc but this hasn't helped.

Test the attached and tell us if you see any difference.uploads/165260/C-PRO-PFD_JohnConnor.dwg

Hi John,Thanks for taking a look. Unfortunately, It is still the same.I have attached a jpg to highlight a few trouble areas. It
just all looks a little bit un-crisp and slightly shabby. Which is not
good when dealing with P&ID's with multiple lineweights etc.If you can think of anything ells that may work, that would be great! I'm starting to pull my hair out! haha.ThanksPeteuploads/11333/Example_for_John.zip

Just how are you plotting to PDF?  Are you using the default AutoCAD DWG TO PDF.pc3 or something else?I printed your drawing from directly from AutoCAD.  Next I created a PDF using the DWG TO PDF.pc3 default in AutoCAD.  I opened the PDF then printed it.  I compared the two.  There was no difference on my end.My guess is either it is a printer driver problem or the fact that you are using some other program to create and print your PDFs.
John Connor2014-06-13 14:08:47

Just using the standard 'plot to pdf' option

How did it look once you plotted to pdf at your end John? Were the lines looking strange?I
have a feeling it may well be my adobe reader. I have opened and
plotted the drawing to pdf using Trueview as well, and the problem is
still there! So It can't be Autocad. It must be the pdf reade.Would you agree?

No, the lines did not look strange at all.  The two prints look identical.Yes, I suppose it could be the version of Adobe Reader you are using.

I'll dig further and see if I can find the problemThanks for your help anyway 

OK...good luck.