there are many free pdf creator softwares for windows os, but most of them are sharewares. they usually put ugly watermark in generated pdfs and limits the number of created pdf pages.im going to enlist two softwares those are my favourites.

1.PDFCreator

this is the favourite tool of mine. it is a free and open-source pdf creator which adds a pdf printer to windows, without any ugly watermark in created pdf files. it has a lot of configuration options which you can tweak to your heart's content, but the default configuration is enough for get going.

pdfcreator is available from http://pdfcreator.sourceforge.net 

2.OpenOffice.org

openoffice.org is a full-blown office suite thats completely free and compatible with MS-Office files(in most cases). it has the ability to create pdf files natively retaining all the bells and whistles you create in your office document.

openoffice is available from http://openoffice.org