I keep notes in markdown in a local folder and sync across machines with git. I tend to use VS Code to edit/read because I like the way its search feature works

I keep notes in markdown in a local folder and sync across machines with git. I tend to use VS Code to edit/read because I like the way its search feature works, but really any text editor would work fine. I sync with a private github repo, but any git remote would be equivalent. Git history and did tracking is obviously more useful for text-based formats like md than it would be for PDFs, but there's no reason you couldn't include PDFs or other small binary files alongside your notes in the repo.