Sorry, I am a PC user, not Mac. The Swiss National Association of and for the Blind supposedly offers a Mac version of its free VIP PDF Reader - but I am unable to find it on their mostly german-language website (http://www.szb.ch/), and I am not sure it is available in an english version.
My understanding is that virtual machine software like Parallels Desktop or VMWare Fusion will allow PC software to run on a Mac, but having not tried it I can not say for sure. For PCs, there are several options. JAWS (http://www.freedomscientific.com/jaws-hq.asp) is probably the most popular PC screen reader, but it costs $. NVDA (http://www.nvaccess.org/) is a free JAWS alternative. There are also free options that let you see what a screen-reader-user would hear: PAC 1.3 (http://www.access-for-all.ch/en/pdf-lab/pdf-accessibility-checker-pac.html) is my personal favorite; Its future replacement - currently beta - PAC 2.0 (http://www.access-for-all.ch/en/pdf-lab/pdf-accessibility-checker-pac.html); And VIP for PC - if you can find it.
Hope this helps.
a 'C' student
Also, I learned that Callas offers a Mac version of their useful free Acrobat plug-in, pdfGoHTML. This is another tool that lets you see what an assistive technology user would hear. You can read about it - or watch the video - here http://www.callassoftware.com/callas/doku.php/en:news:press:20121119, and download it here http://www.callassoftware.com/callas/doku.php/en:download.
Thanks! I'll check it out!