Ale,

The problem you have already have been discussed here on the Forum several times.

I cannot find all topics now, but here is one of them:

https://forums.autodesk.com/t5/autocad-for-mac-forum/strange-lines-and-joins-in-pdf-export/m-p/43498...

Look for the answer in #2 of my post there.

The problem is that you are trying to fit large objects on a small piece of paper. In order to achieve this you need to downscale them strongly, as the result AtoCAD cannot handle such resolution in PDF output.

Maxim