Reading and annotation apps: highlight, annotate, and review PDFs on your phone.
Put Rodrigo Pereira
Highlighting a PDF on your phone is just one step in the revision process. Afterward, you need to find the passage again, consult the annotation, and transfer the material to another device. In reading and annotation apps, these functions can make more of a difference than the variety of highlighter colors. This guide compares tools based on official fact sheets and resources documented by developers.
Two examples of what the store offers today: Evernote, free for 50 notes and 1 notebook, syncing on a single device; Goodnotes, no longer exclusive to the iPad, runs on Android and offers a limited number of notebooks for free. Those who choose the app for its reputation discover the limitation halfway through the exam.
I'll break it down by task: PDF, e-book, handwritten notebook, and quick note. For each one, I'll explain what the free plan includes and how to review what you've highlighted.
Highlighting is easy; reviewing is what sets the apps apart.
Highlighting takes a tap. The problem arises three weeks later, when you need to gather what you've highlighted from four PDFs and two books to create a summary. That's where three features come in that not every app has: a list of highlights separate from the text, a search function that looks within the notes (including handwritten ones), and synchronization that transfers everything to your tablet or computer.
When I'm evaluating a note-taking app, I ask in this order: Does it show the highlighted notes in a list? Does it allow you to export that list? Does it find a handwritten word? Does it save everything to the cloud for free? An app that makes nice markings but doesn't answer any of these questions is like a battery-powered highlighter pen.
Choose by the task, not by the name.
The table summarizes what I checked on the app pages in September 2026. Ratings and downloads are from Google Play; what's included in the free offer comes from each app's official description or the developer's plan table.
| Task | App | What does "free" include? | How to review |
|---|---|---|---|
| PDF of a textbook or contract | Adobe Acrobat Reader | Highlight, comment, fill in, and sign. | List of comments; the shared file bears the following marks. |
| E-book purchased | Amazon Kindle | Synchronized reading, highlighting, and note-taking. | Notebook by book, in the app and on the computer. |
| Standalone e-book or PDF, offline. | ReadEra | Everything; the record says there is no advertising or internal purchasing. | Markers and position saved by file |
| Handwritten notebook | Goodnotes | Notebooks in limited numbers; writing and searching in the handwriting. | Search within handwritten text; synchronize between devices. |
| Handwritten notebook (alternative) | Microsoft OneNote | Everything, with a free Microsoft account. | Handwritten notes become searchable content. |
| Structured note | Notion | Personal and student use without paying. | Tables, databases and search |
| Structured note (classic) | Evernote | 50 notes, 1 notebook, 1 device | Searches and notebooks; the limit is reached quickly. |
| Quick note | Google Keep | Everything, with a Google account. | Markers, colors, and search. |
PDF: Acrobat Reader highlights, comments, and signs without paying.
For textbooks, scientific articles, and contracts, Adobe Acrobat Reader remains the go-to tool, and the Play Store page differentiates what's free: adding notes, comments, and text highlighting, as well as filling out and signing documents with Fill & Sign. What's available for the Premium subscription is editing PDF text, creating, converting, compressing, and using the AI assistant. For studying, the free version is sufficient.
The key detail that makes the revision: each highlight and comment is saved within the file itself. When you share the PDF via email or WhatsApp, the annotations are included and open in any reader. The list of comments shows all the notes in sequence, with the page number for each one, and this is the fastest way to create a summary.
Adobe Acrobat Reader: Read PDF
AndroidAnother reader with markup capabilities is the PDF Reader: Xodo (rated 4.7 on Play, 10 million+ downloads) which highlights, underlines, draws, inserts text, and signs. The listing doesn't differentiate between free and paid features, so check the plan within the app before relying on format conversion.
Step-by-step: highlight a PDF and transfer the highlights to the summary.
- Open the PDF in Acrobat Reader and tap the pencil button, then click Comment. Choose the bookmark and drag it over the passage.
- For each important highlighted section, tap on it and add a short comment explaining why it matters. This is the comment you will read during the review, not the entire passage.
- Open the list of comments (speech bubble icon). It shows the highlighted sections in page order. Just read that and you have the outline of the summary.
- Share the file with yourself (Drive, email) or copy sections of the list into your notes app. The highlighted version is the one that counts; don't redraw the marks in another copy.
E-book: Kindle synchronizes highlights; ReadEra reads everything offline.
On the Kindle, what's useful for studying is Whispersync, which Amazon describes in its listing: last page read, notes, bookmarks, and highlights synchronized between your phone, tablet, Kindle, and computer. You highlight on the bus and find the same highlights on your laptop at night. Inside each book, the notebook icon gathers all the highlights and notes, and you can share this entire list at once.
This guide treats the Kindle only as a bookmarking tool. The catalog, what's free, audiobooks, and reading for leisure are covered in the other guide. app guide for reading and listening to books, which compares subscription prices.
Amazon Kindle
AndroidFor PDFs and EPUBs you already have on your phone (professor's notes, university portal articles), ReadEra opens PDFs, EPUBs, DOCs, DOCXs, MOBIs, AZW3s, and more, works offline, and, according to its own description, displays no ads or in-app purchases. It automatically detects files, saves bookmarks and the page where you left off, and opens two documents on the same screen. Rated 4.9 on the Play Store, with over 50 million downloads.
Handwritten notebook: Goodnotes searches within your handwriting.
For years, Goodnotes was a paid app and only available on the App Store. Today, its listing on the Play Store shows Goodnotes: AI notes, docs for Android, Chromebook, Windows, and web, free to download, with a 4.1 rating based on nearly 35,000 reviews. App Store, Goodnotes: AI Notes, PDF has a 4.8 rating based on 79,000 reviews and is also free to install.
Goodnotes combines handwriting and PDF markup, with search and features that depend on platform, language, and plan. Installing for free doesn't necessarily unlock all notebooks and functions. Before migrating your notes, test a note, search, and export on the device you'll be using; check the limits displayed in your account.
Goodnotes: AI notes,docs
AndroidAn alternative with unlimited notebooks: Microsoft OneNote, free with a Microsoft account. The description says that handwritten notes and photographed pages become searchable content. It has a 4.7 rating on the Play Store and over 1 billion downloads. Both apps work with a finger, but it's the stylus (S Pen, Apple Pencil, or a generic one) that makes the handwritten notebook worthwhile.
Structured note-taking: Notion (free for personal use); Evernote with 50 notes.
Notion organizes material into pages and databases: author, topic, reading status, and citations can all be in one place. The free plan caters to personal use, while collaboration and other features have their own limitations. In compatible apps, you can download pages for offline use; paid plans also offer automatic downloads of recent and favorite pages. Prepare your material before you lose connection.
Notion: notes, tasks, and AI
AndroidEvernote was the standard in its category for years and still performs well within images and PDFs. However, the Free plan, according to the official plan table, offers 50 notes, 1 notebook, synchronization on 1 device, and 1 GB of storage. Fifty notes disappear in a month of classes. If you already use it and fit within this limit, continue; to start today, Notion, OneNote, or Keep offer more without charging extra. The 4.0 rating on Play is the lowest on this list.
Quick note: Google Keep captures and finds later.
When an idea pops up in the middle of class, you don't open a database. You open Keep. It's from Google; you log in with the account your Android device already uses, and the app summarizes what it does: notes, lists, photos, voice memos with automatic transcription, reminders integrated with Google Tasks. Tags and colors organize; the search function finds everything. Photograph the professor's slide, and the note saves the image along with the text.
Google Keep: notes and lists
AndroidKeep doesn't replace a notebook: it's just the entry point. Once a week, what's in Keep goes into Notion or a handwritten notebook. And what becomes a task with a deadline is removed from Keep and goes into a task app; I compared the free plans in the article about it. The 5 best apps for organizing tasks..
Review: the routine that makes highlighting pay off
Marking without reviewing is the most common mistake, and no app fixes it on its own. What works for me is a short routine, on the same day of the week:
- Open the list of comments for each PDF highlighted during the week and the Kindle highlights notebook. Read only the lists, never the entire text.
- Copy the passages that still seem important a week later into a single note (Notion or OneNote). Half of it doesn't seem important; that's how the summary gets leaner.
- Write, in your own words, one sentence for each copied passage. This is the sentence that the examiners will find the day before the exam.
- Check if it's synced: open the note on your computer or tablet. If it doesn't appear there, it's stuck on your phone, and you'll find out at the wrong time.
This routine is one layer of a larger system, with calendar, tasks, and notes working together; I described all three in... Organization and productivity apps guide.
What your phone can already do without installing anything.
On iPhone, the Files app opens any PDF and the Markup button highlights, underlines, and writes over it; the Books app saves ebooks with highlights and notes; the Notes app accepts handwriting. On Android, Google Drive opens PDFs with a pen and highlighter for annotating over them, and Keep covers quick notes. Samsung devices include Samsung Notes, which imports PDFs and allows writing with the S Pen.
What the system doesn't do well is search within a handwritten notebook and gather highlights from different files; that's why Goodnotes, OneNote, and Acrobat remain on the list. And if the notes are printed, the way to go is to scan them before highlighting: apps that perform OCR and generate clean PDFs are available on [website/platform name]. Scanner app guide for scanning documents.
Mistakes that make the highlight disappear
- Highlighting in one app and opening in another. Acrobat highlights remain in the PDF; Kindle highlights remain in your Amazon account. Mixing readers loses half the value.
- Turn off syncing to save data. If your phone is swapped or lost, you'll lose your semester too.
- Highlight everything. If a page has 40% in yellow, the list of comments becomes the text itself. Highlight the sentence that summarizes it and write the reason in the comment.
- Open eight notebooks in Goodnotes for free or 60 notes in Evernote for free. Count them beforehand; the limit is determined by the notebook's availability, not your needs.
- Installing a PDF reader from outside the app store because it promises free editing. Outside of the Play Store, there's no Play Protect or updates, and signing a contract in an unknown app puts your information in the hands of a third party.
How do these apps make money?
All the apps in this guide are free to install, and the billing process differs. Adobe, Goodnote, and Evernote sell subscriptions: the free plan covers reading and annotation, while payment unlocks editing, conversion, unlimited notebooks, or more notes. Notion and OneNote charge companies and teams; individual users are the entry point. Amazon profits by selling books: on Kindle, the app is free, but the content is paid. ReadEra states in its description that it doesn't sell anything within the app. Knowing this avoids the surprise of a blocked button in the middle of the guide.
Common questions
Can I transfer my Kindle highlights to the Notion?
Yes: in the book, open the notebook (notebook icon), share the list of highlights with yourself, and paste it onto a page in Notion. Notion's search function will then be able to find any passage.
Do I need a pen to use Goodnotes or OneNote?
Not to mention: both accept the finger. The pen changes the legibility and speed, and without it, searching in the manuscript is more prone to errors. For those who only highlight PDFs, the finger works.
Is Evernote still worth it on the free plan?
For those who can fit 50 notes and 1 notebook on one device, yes. For students with multiple subjects, the limit is reached in weeks. Notion or OneNote cover the same usage without this limit.
Does Acrobat Reader edit PDF text for free?
No. Highlighting, commenting, filling out forms, and signing are free; editing text, converting, compressing, and the AI assistant are part of Acrobat Premium, which comes with a 7-day trial.
Will my griffins disappear if I change my cell phone?
It depends on where they are stored. Kindle, Notion, OneNote, Evernote, and Keep save to the account and restore to the new device. PDFs highlighted in Acrobat or ReadEra are archived files: they need to be in Drive, iCloud, or a backup.
First step today: take the PDF you most need to study this week, open it in Acrobat Reader, highlight five passages with a one-line comment on each, and open the list of comments. If the list alone explains the subject, you've found the method; the rest is choosing where to save it.
