Free Snipping Tool only has one version in which pro features can be activated after you buy and apply an activation key in Free Snipping Tool settings.
Step1: Buy key from this page
Step2: Open activation form.
Step3: Copy key and click Activate button and wait.
Step4: Wait for this to activate your software, then exit and restart Free Snipping Tool.
Step5: Now restart app and confirm activation in Settings>About.