Lecture notes and the slide they are about
Note-taking for people being taught something: handwriting over a document, audio recorded against it, and the source material kept where it can be seen.
Studying is a two-document activity. There is the thing being explained — a slide, a chapter, a score, a paper — and the thing you are writing about it, and the value is in the relationship between them. Every app here knows that, which is why they all annotate rather than just record: the note is placed on the source.
On one column that placement gets expensive. Writing on a slide means the slide is the size of a phone; writing beside it means switching. Several of these apps solve it by recording audio while you write, so the lecture can be replayed against the note later — a good answer to a problem that is partly about screen size.
Unfolded, the source and the note can be the same view at a size you can write on, and the recording goes back to being a safety net rather than the plan.
- 1
Notability: AI Notes & PDF app
Ginger Labs, Inc.
Handwriting, typing and sketching over PDFs, textbooks, lecture slides and images, with audio recorded alongside and notes made searchable afterwards. It is the most direct statement of the problem on this list: the app exists because the note and the document it is about belong on the same page.
- 2
Goodnotes: AI Notes, Docs, PDF
Notes & PDFs · Goodnotes Limited
Handwritten notes and imported documents, with search across handwriting and a whiteboard for the parts that do not fit a page. The handwriting is the reason it is here — a pen needs physical room, and the room it needs does not shrink just because the display did.
- 3
Noteshelf: AI Notes & PDF
Fluid Touch Pte. Ltd.
Lecture and class notes with lifelike pens, annotation of worksheets and slides, recording while you write, and output to an external display. An app built to be driven while somebody is talking is one where every extra second spent navigating is a sentence missed.
- 4
Microsoft OneNote
Microsoft Corporation
Notebooks, sections and pages, with voice transcription and search across the lot — the most hierarchical app on the list. Hierarchy is only an advantage while it is visible; collapsed into a navigation screen it becomes one more thing to remember.
- 5
PDF Expert: Editor & Converter
Readdle Technologies Limited
The reading half rather than the writing half: the set text, highlighted and marked up, with the outline and thumbnails for getting around it. Working through a chapter is a job of going back and forth, and going back and forth is cheap when both ends are on screen.
- 6
Readwise Reader
Readwise, Inc
Articles, papers, newsletters, PDFs and EPUBs collected into one queue, built for people who read a lot rather than occasionally. Reading at that volume is as much about managing what is waiting as about reading it, and the queue and the page want to be visible together.
- 7
MuseScore－Sheet Music & Chords
MuseScore Limited
Scores for whatever you are learning to play, viewable and playable online or off. Practising from a screen is the same constraint as reading from one, except that you are holding an instrument and cannot keep adjusting the page.
The selection and the order are ours. Each entry is written from that app’s own App Store listing, linked beside it, and this page from Apple's iPhone Duo product page. Drafted with AI assistance and checked back against those sources before publishing; the disclosure page explains how. The iPhone Duo has been on sale since 23 October 2026 and nothing here has been seen running on one, so what each entry says about the fold is an argument rather than a test.