PowerPoint 2011 for Mac: How to Save As PDF and Hide Hidden slides?
Instead of Save As... PDF, Print->"Save as PDF".  You can get around the print margins by setting up a printer/presentation that has no margins, "full bleed". 

A few important steps:


First, go to File -> Page Setup and make sure that you've got the dimensions there identical for the default paper size in the printer.  In my case, it's 8.5 x 11 inches for Letter size paper.  Read the dialog box carefully, and select the option that lets you set a size larger than the printer will allow.
In the print dialog, make sure you do NOT have "scale to fit paper" checked.


You should now see that the print preview in the print dialog is edge to edge.