Doxillion is a free software to batch convert files to PDF. It is free for non-commercial home use only.
It contains Add File(s) and Add Folder options to add files to convert them. After adding files to its interface using either of these options, you need to specify the output format as PDF and also set the desired output folder. Now, clicking on Convert button begins the process of PDF conversion.
It supports a variety of document formats including Microsoft Word, Excel, Works, XPS, Apple Pages, Open Office, HTML, CSV, TXT, RTF, XML, and also some popular image formats: JPG, BMP, GIF, PNG, PCX, TGA, TIFF, etc.
It even lets you batch convert any of supported files to other formats including: DOC, DOCX, HTML, ODT, RTF, TXT, XML, etc.