Today I had to convert hundreds of .doc files to .pdf. I first thought it would be impossible because there would be not such option or command line option on MS-Word. But surprisingly, this great tutorial shows how using powerful command line arguments for MS-Word.
http://raywoodcockslatest.blogspot.com.br/2012/03/batch-converting-many-microsoft-word.html
From the page above (with a little change):
FOR /F “usebackq delims=” %%g IN (`dir /b “*.doc”`) DO “C:\Program Files\Microsoft Office\OFFICE12\WINWORD.EXE” “%%g” /q /n
/mFilePrintDefault /mFileExit && TASKKILL /f /im winword.exe
this batch will get all the doc files on a directory and convert them to PDF by using the default printer, which is configured to print to PDF files.
Yet Another Technology Blog 