Yes, the product supports for XLS file format. According to the description, you can use it with the following formats: PDF, HTML, XHTML, RTF, Excel, JPEG, GIF, BMP, EMF and WMF. As you can see, there is Excel listed which means XLS is a supported format.
To find additional information about the software, visit the following link: http://rarefind.com/rbpro/index.html
On the website you will have the possibility to check for documents, buying options and other related resources.