I've checked the software but there was nothing mentioned about the Combine function, however since this is a PRO application that allows you to edit PDF files, you can simply append PDF files to already opened PDFs, which means that in a way or another the software works as it should and it lets you add other PDF files to combine them with the ones you already have created or opened within the application.
For additional information, I recommend using the official website to learn more about it: http://www.pdfpro10.com/
