Write on your PDFs with Apple Pencil

Some reading only happens with a pen in hand. A question mark in the margin, an arrow from a claim to the figure that's supposed to support it, a quick sketch of how an argument fits together. Highlights and typed notes are good at a lot of things, but they aren't good at that.

So the ScholarThread app for iPad and iPhone now lets you write directly on the PDFs in your library, with Apple Pencil on iPad or with your finger on iPhone.

How it works

Open any PDF in the reader and tap the Pencil button in the toolbar to turn on ink mode. You get Apple's own drawing tools, the same palette you already know from Notes and Markup: pens, an eraser, the lasso for moving things around, and the rest. Tap the button again when you're done. In scrolling view your ink stays on the page; it just isn't editable until you turn ink mode back on.

On iPad, only Apple Pencil draws. Your fingers keep doing what they always do: scroll, pinch to zoom, turn pages. So you can rest your hand on the screen and move around the paper without leaving stray marks. If you use your Pencil's double-tap or squeeze, they do whatever you've set them to do in iPad Settings. On iPhone there's no Pencil, so in ink mode your finger draws.

There's no save button. Ink is saved automatically a moment after you stop writing, and again whenever you leave the app.

Your ink stays where you put it

Handwriting is only useful if it stays attached to the line it's about. Ink in ScholarThread is pinned to its exact spot on the page, not to the screen, so it stays put when you zoom in on a dense table or zoom out to see a whole page. It's redrawn sharply at every zoom level, too, so a note written zoomed-out doesn't turn into a blur when you look at it closely.

A few details worth knowing:

• Every PDF on a paper can have its own ink. If a paper has a main article and a supplementary PDF, you can write on both, and each keeps its own handwriting.
• Ink lives in scrolling view. If you read in page-flip mode, turning on ink mode switches to continuous scroll while you write, and turning it off puts page-flip back. For now, page-flip mode doesn't show ink, so read in scrolling view to see your handwriting.
• Dark reading themes adapt your ink, so black handwriting stays readable on a dark page.
• It works offline. Ink is saved on your device first, so once a PDF is downloaded you can write on it on a plane or in a library basement, and it syncs when you're back online.

On every device, and on the web

If you're signed in, your ink follows you. Write on a paper on your iPad, and it's there when you open the same paper on your iPhone. When you open a PDF while online, ScholarThread fetches the latest ink for it.

If you edit the same page on two devices before they've had a chance to sync, the version you changed most recently wins. Edits that are still waiting to sync aren't overwritten by ink arriving from another device; they're kept until they can be sent.

In the web reader on your computer, your ink appears on the page exactly where you wrote it. On the web it's read-only, and a Show ink switch lets you hide it when you want a clean page. Writing still happens on the iPad or iPhone, where the Pencil is.

If you use the app without signing in, your ink is kept on that device. Sign in later and it moves to your account along with the rest of your library.

What ink is, and what it isn't

Ink in ScholarThread is your handwriting, kept exactly as you wrote it. We don't run handwriting recognition on it, and the AI features don't read it: chat and assisted notes never see your drawings.

It belongs to the PDF it was written on, so:

• If you replace a paper's PDF with a different file, the ink saved to your account for the old file is removed. It was written on pages that may no longer line up.
• If you delete the PDF or the paper, its ink is deleted from your account and from the device you deleted it on. If another device has handwriting on it that hadn't synced yet, that device keeps it until you delete it there too.
• If you delete your account, the ink stored in your account is deleted with the rest of your data. Ink already on a device stays there until you remove the app or use Reset to factory defaults in Settings.

Ink works on PDFs only. EPUBs reflow their text to fit the screen, so there's no fixed page to write on.

Where it isn't yet

Writing with ink is an iPad and iPhone feature. The Android app doesn't support ink yet, and on the web you can see your ink but not add to it.

Getting started

Ink is in the latest version of the ScholarThread app on the App Store. Open a paper, tap the Pencil button, and start writing. If you're new to the reader, the workspace tour covers highlights, notes and the rest of what you can do with a paper, and our note-taking workflow shows how to turn what you read into notes you can use.

If something doesn't behave the way this post says it should, tell us. Ink is new, and we'd rather hear about it than guess.