novaPDF can be used for up to 30 days for free. During the trial, you have all the functionality of the installed edition, but each page of the resulting PDF will show a footer notice. After 30 days, the program will no longer work, unless you purchase a license and activate it. The licensed version doesn't expire and doesn't add any footer notices.
novaPDF requires the .NET framework (version 4.6 or higher) to work, so you'll be prompted during setup to install if it's not already on your PC.