I don't pretend to understand but from what I have read just now there seems to be some requirement for a printer when attempting to convert spreadsheets to PDF files.

What I read offers a utility called novaPDF which is "installed as a virtual printer so you can create PDF files simply by printing to it instead of your normal printer".

It's a workaround, so may not be ideal, but if you want to try it, the full article is here;
http://www.novapdf.com/kb/convert-excel-to-pdf-microsoft-excel-spreadsheets-to-pdf-206.html

I hope that helps.

Mark