Method A (only for Office 2007) :
Download and install the Office Addin: 2007 Microsoft Office Add-in: Microsoft Save as PDF or XPS (http://download.microsoft.com/download/f/4/b/f4bfd843-a0b6-4031-aa98-0a3db7403d0f/SaveAsPDFandXPS.exe ) so that you can save your word files as pdf files directly after finishing.
Method B (for Office 2000, 2002, 2003, 2007 and 2010):
Use the free Office to pdf converter Moyea PPT to PDF Converter
http://www.dvd-ppt-slideshow.com/ppt-pdf-converter/
to convert your word files to pdf files directly.
Method C (only for Office 2010):
If you are using Word 2010, you can save the Word files to pdf files directly.