All you need is a virtual printer which can create PDF files. It's also called a virtual PDF printer. This virtual printer is used in the same way as any other printer in Windows, with the difference that the PDF printer creates PDF documents.
A free and easy to use PDF printer can be downloaded from this page. Just click the "download" link to the right of this article to download the latest PDF24 Creator which installs for you a virtual PDF printer to print to PDF.
This PDF printer has a Word to PDF function. To print a Word document to PDF do the following: Open the PDF24 Creator and drag & drop your Word document into the right-hand area of the window. The Word document will be converted to PDF if you have Microsoft Word or another Word document reader installed.
Another way to print the Word document to PDF is to open the document and manually print it on the installed PDF24 PDF printer. This prints to PDF too.