The difference between Free and Pro versions is very vague, to say the least. What, exactly, is left behind with the free, for instance?
The 'cleaning' is the same with both free and pro versions.
The differences between free and pro versions are mainly in scheduling, monitoring, and the cleaning of multiple user accounts.
https://piriform.zendesk.com/hc/en-us/articles/204043904-Benefits-of-CCleaner-Professional
If you have the free version installed then go to 'Options' and look at the tabs for "Settings", "Scheduling", "Monitoring", and "Users".
You will see that certain options have the word “PRO” and a padlock symbol next to them.
These settings are only available in the Pro version.
The Pro version also gives you a licence key which entitles you to priority email support from Piriform.
suppl.
there is a pro plus -> 4 in 1 (ccleaner, defraggler, speccy and recuva)
How many computers can I install CCleaner Professional on?
Note: If you bought a boxed copy of CCleaner Professional at a retail store, you may be able to install it on more than one computer. Please check the box/packaging for more details.