Minor updates are available at no charge for standard licensed software. (Not for trial versions, which are only good for a short time anyway). More significant updates can be purchased for a upgrade fee which is substantially less than the cost of new software.
The software checks for updates automatically when you start it. If there is a newer version for which you are eligible, it will display a list of the changes in the most recent releases. You will then be given an option to install it now, later or skip. If you choose to skip an update, you will not again be asked on startup if you want to update. If you decide later that you want to install the update, you can use the Check for Updates... menu operation. This is on the Help menu on Windows and the RATS menu on the Macintosh.