20th century digital standards like JPEG, PNG and MP3 (date?) are fully documented, still widely supported by modern software, and likely to remain so for ages. I think old PDFs are still ok.
Smarter/richer standards like DOC or flash from that era are now occasionally unreadable by the modern software. You may have to resort to a VM and "now you have two problems".
Actual media from 20 years ago might not be readable. You definitely need a rolling program of copying to new media. Fortunately, sizes appear to be growing faster than the years are adding new content, so this isn't a problem until civilisation has one of its every-millennium-or-so resets and we lose both the industrial means to support the media and the cultural means to understand the language/format.
The latter may not seem like a big problem until you realise that, despite all the clay tablets from 1750BC, we have no idea what any music sounded like prior to the late Middle Ages.