Yes, the application is really free and it can be used to convert the files, as described on the official website. I've tested the product and I didn't encounter any nag screens or limitations, but I experienced something weird which I believe it was normal. I converted a PDF file that had tables and the resulted DOC file opened correctly, but it was almost impossible to edit it in a compatible Word processor.
For simple PDF files with text, it should work flawlessly.
