Have a look here to see a view options: https://stackoverflow.com/questions/3022376/how-can-i-convert-a-word-document-to-pdf
We have used xdocreport mentioned on the link to achieve this with good results although it wasn’t as fast performing as we would like.
In one of my projects i’ve used Aspose. Aspose has a commercial jar that can do conversions in enterprise quality and PDF-A format, but it does come with a pricetag.