Depends on what the OP is doing. Some people just have repeated tasks of preparing documents. I don't see any security implications of using 7-year-old software as long as the user is just using it for authoring some PDFs and not opening anything of an external origin. The OS, if connected to the Internet, must be up to date though.
That being said I agree that licensing/subscription model makes sense even though I personally hate it too.
I think that just emphasizes we need better desktop application sandboxing.
If I could trivially say this app does not get network access, restricted to this file system directory, can only read the supplied file, etc why should I have to live in fear? Granted, now that everything "needs" the internet quite a few of those limitations are meaningless, but I can dream.
> you are gonna have a bad time from a security perspective
You say that like it's inevitable, but there's no reason to state with certainty that bad things will happen unless you keep paying up.
No doubt software companies benefit from the fear of old versions. The fear spreads via comments like yours. Who wants a "bad time"? Not me, not anyone. The solution is easy! Open wallet, pay now, or better still hand over credit card and keep paying every month. Protection money, turning bad times into good times.
You are not buying a "product". You are buying a license to use the software under some conditions one of which could be that if you use it year after year you must pay more.
Nobody is "forcing you" to pay for updates, they are selling you a license. And since they are the seller they can write the terms of the sale.
I would love to pay for Acrobat from like 7 years ago. There's been no value add for me.