The normal way to create pdfs is to get a good virtual pdf printer. I've used Primo free for some time, very successfully.
The free version doesn't do batch creates per se - but I do batches of .doc files by marking them all, then choosing print from the context menu.
It does mean clicking OK a couple of times for each file but that's not too onerous for a free conversion.
There's a paid version which may have more facilities. It's a free download, so you can readily give it a try.