Adobe's image editing software Photoshop is available for download in a free trial version. The trial lasts 30 days, and you can convert it to a full version at any point by purchasing a full Photoshop license. The license comes with a unique serial number you can use immediately to deactivate the 30-day countdown and access the full, unrestricted version of Photoshop.
Open your trial copy of Photoshop. Before the program starts, a dialogue box will appear displaying the time remaining in your trial. You can also access this box from Photoshop's "Help" menu.
Click the "Purchase" button and follow the on-screen instructions to purchase a Photoshop license from the Adobe Store. You'll be provided with a unique serial number.
Return to the countdown box and enter your serial number in the space provided. You can do this at any point during the trial, or even after the trial has ended. Once you enter a valid serial number, Photoshop will unlock and become full-featured.