PDF file creation

I have a 600kb Word 2010 file containing one pic of 50kb size and the remainder is a 120,000 word book. I select PDF in Save As and wait for the creation of the PDF file. It works and the result is good except the size of the created Adobe pdf file is in excess of 52mb.
I've done many of these conversions in the past and in all cases the resulting pdf file would always be larger, by around 200%, ie from 600kb to 12-1500mb.
Any help/advice/guidance with this 'problem' is greatly appreciated.

Colpubs:confused

 

I have never saved a word doc as PDF, so I have no direct experience. But I have just found this: http://office.microsoft.com/en-us/word-help/save-as-pdf-HA010064992.aspx#BM17 - there seems to be some options you can use that influence the quality & size of the resulting PDF.