Upgrading from CS4

Hello.  A decade ago, a non-profit I was volunteering for bought CS4 Web from TechSoup (I think) for me.  It still works just fine for what I do with it.  I just use Photoshop and Acrobat, mostly.  But it's getting hard to find support when I can't remember how to do something, which is more and more often these days.  Note that I had trouble finding an appropriate forum to post this question in!  So I thought I'd try to find out if I can upgrade.  Is there a way to purchase an old version of CS that is available without taking a chance on some used version from EBay?!  I am retired now and on a fixed income.  I used these products now and then:  Trying to fix up old photos for my church or my fellow veterans, cleaning up a document for the church website, or just brightening up a photo for my FB page.  I don't want a monthly subscription  bill for something I don't even use monthly.  Is Adobe no longer viable for casual users?