When I Export to PDF using the Export command in 2015 AutoCAD LT for Mac I get no output whatsoever, no matter what printer is set as defaut.

Instead, I have had good success using an older open source printer called PDFwriter for Mac. Evan Troxel had a good post on how to set up on his site, Get Method. Here is the link: http://getmethod.com/blog/printing-large-pdfs-on-a-mac.

It has all of the typical large format paper sizes and works with the Batch Publish command. Here is the sourceforge download link:

http://pdfwriterformac.sourceforge.net

-Bill