How long has Adobe PDF been available? Is this file format still relevant today and is likely to be used in the future?

Many media- agencies use it still. So yes, still relevant.

It has been around in one form or another for 20+ years.

It will be around forever because of the sheer number of documents that use PDF format.

Another reason it will be used forever is because it is an international standard (ISO32000) link which means that it is a required format for many international documents.

First released on the 15th June 1993.

I’ve used it off & on for 20 maybe 25 years. I began looking for alternatives probably 10–15 years back when it became vulnerable to hackers. I currently use Foxit which is free to use & I like much better than adobe. Since adobe set the standards, I think it will be relevant for a good while. Still, in today’s climate of hit & run, I can see it being overtaken by one of its rivals!!!