Personal knowledge management or PKM is the art of taking personal responsibility for the knowledge that you need to refer to in going about your daily life.
It is a skill and discipline similar to what a librarian or museum curator may perform in their role, but differs because personal knowledge management has to reflect your personal view of the world. Knowledge management has different scopes.
PKM is knowledge as YOU need it to be.
There is a journey here. What works for you today, will not work for you tomorrow. As the number of document expands the links between them become richer and there is more to mine for inspiration. There will also be some dark corners - places that have not been visited for some time and may be just forgotten or now stale.
Don't chase the perfect system. All you need is the system that works for you now.
Typically, Personal knowledge management is done using Personal knowledge management software but that does not have to be the case and many paper-based systems exist.