I have Photoshop CS2 and if I want to get a newer version I have to subscribe and pay a monthly fee.
But if you have version "4" want to upgrade to CS 2 you may still be able to do that for free.
When they decided that they were not going to let people reinstall their older software that they had paid for, there was such an outcry of discontent that they made CS 2 available for free.
If you find it do what I did and create a DVD of the install program with the serial number on it.
If I can find it I will come back with a link, I have posted it here before.
Mike
Here's my old post...
www.windowsforum.com/threads/adobe-photoshop-for-free-it-may-not-be-for-long.223440/
It appears to still work, I'm on my tablet so I can't be sure.