Notability is the handwritten-note benchmark from US-based Ginger Labs, launched in 2010 with 15M+ downloads, known for low-latency Apple Pencil writing, audio-synced recording and PDF annotation across iPhone, iPad and Mac.
RemNote is a notes-plus-memory tool for students that deeply combines note-taking with spaced-repetition flashcards, supporting PDF annotation, bidirectional links, and multi-platform sync, free tier available and Pro about $8/month.
Nimbus Note is a feature-rich note and team knowledge base app supporting web clipping, PDF annotation, nested documents, and kanban boards, with a free plan for personal knowledge management and team collaboration.
Logseq is an open-source local-first note-taking app launched in 2021 by a US team, built around outlining and bidirectional links; notes are stored as Markdown files locally with PDF annotation and whiteboard support, a popular choice for building personal knowledge bases.