Pretty much everything you need to get by in the imaginary post-apocalypse world (which will be littered with consumer goods for a long time) you can find the Boy Scouts Handbook. The normal human solution to not knowing how to do or make something (historically) is to find someone who does and partner or barter with them. Trying to collect and carry around all of the world’s knowledge seems the least plausible way to go.
There are plenty of other things that would be more difficult make, source, or do. How do you preserve food to modern standards if you don't have canning lids and can't make them, refrigerators don't work (some climates might not matter as much), or a local salt/nitrites source? Fermenting is one way, but doesn't work for everything.
In a society with soap-making potential (this is a fun categorisation) you'll need materials and capability. If you're in that situation, I sincerely doubt PDFs are going to be useful unless they've already been printed and/or frequently discussed, i.e. books and stories.
Maslow's hierarchy of needs may have issues, but it's surely a useful heuristic.
They are a wealth of information and quite common through to ~20 years ago. I imagine sets of these will remain somewhat common for another 100 years in peoples garages or on display etc.
Take soap for instance. People have made soap since the dawn of time - you just need fat and lye. But how do you actually.. do it?
For that you need instructions, which means either a library of books vulnerable to all sorts of ills, or a collection of pdfs and movies. If you go the digital route you need some kind of viewer.