Word 2007 will save as PDF (assuming that it is updated to at least SP2).
https://www.microsoft.com/en-us/down....aspx?id=27838 Check the ISO 19005 option and it should handle your equations.
PrimoPDF is one of the better free versions, but if it is not working for you you could try PDF Creator. I prefer the older less bloated version 1.7.3 -
http://www.npackd.org/p/org.pdfforge.PDFCreator/1.7.3, but if you are trying this product (any version) be aware it comes packaged with all sorts of chaff and 'free options' that will screw up your browser so take care that you only install the core program.
The best option is Adobe Acrobat, but $50 it is not.