There have been quite a few discussions on this forum about CTB files. Can I use them? Can I edit them? The answer is yes.
If you configure your page setups correctly, output to PDF is exactly the same as printing to a printer. All line weights are displayed just as you would expect.
The place to edit your CTB files is in the page setup manager. Here is a quick run-down of how to get there - I'll leave the rest up to you...
Type PAGESETUP at the command prompt or choose Page Setup Manager from the File Menu.
Select the Page Setup you'd like to edit and then from the gear menu (next to the +/- buttons) choose Edit.
A Page Setup window will appear. If you don't see any Plot Style Table options on the right-hand side, click on the small disclosure triangle just to the right of the OK button at the bottom of the window. This will reveal the advanced options.
You should now see the plot style settings. Here you can edit CTB files and control your line weights. Make sure you save all changes as you go and if you want to use plot styles, please make sure you select "Print with plot styles".
Attached are a couple of screen shots of my settings. I'm using AutoCAD for Mac 2012 on OS X Lion 10.7.2 but the settings should be the same if you are on Snow Leopard.
Hope this helps those out there still getting use to AutoCAD on the Mac. Happy holidays!
Pretty straight forward through the plot styles folder (within Autocad) which opens up the folder containing the ctb,stb,etc. files. Just make a duplicate of the original ctb file and then edit the original ctb file to your preference of pen,colour, width,etc. settings. Took me about 10 minutes to finetune it to my preferred settings and it works fine with plots and saving/creating PDF's.