PDF Annotator: How to Annotate and Write on a PDF File
Aug 28, 2025
4 min read
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Looking for a way to annotate and write on PDF files online? With Glasp’s free PDF annotator, you can highlight sentences in different colors, take notes, and even generate AI-powered summaries — all directly in your web browser.
This makes Glasp an excellent tool for:
Students taking notes on textbooks and research papers
Professionals reviewing contracts, reports, or presentations
Lifelong learners keeping track of insights across reading materials
In this tutorial, we’ll walk you through how to annotate a PDF with Glasp and keep all your notes organized in one place.
👉 Related: How to Upload and Highlight Local PDFs on Glasp
Step 1: Install the Glasp browser extension
As mentioned above, we will use Glasp to annotate PDFs. So, first of all, please install the Glasp browser extension. It's available on Chrome, Safari, Brave, Edge, and Opera.
👉 Glasp - Chrome, Brave, Edge, Opera
After you install the extension, please pin it to the toolbar so as not to lose it.
Step 2: Sign up for Glasp
To use the annotation feature, you need to have a Glasp account. It keeps all the annotations you made, and all the notes, and allows you to export them into a note-taking app with one click.
Click the Glasp icon on the toolbar. It opens a sidebar on the right. And you can see Log in / Sign up, so please click it and create an account.
If you're taken to the Home page after sign-up, please choose any topic you're interested in up to 10. You can update it anytime later. If you don't see this page, please ignore this step.
Step 3: Open a PDF in a web browser
Glasp supports web-hosted PDF files to annotate at this moment. So, please open a PDF in the web browser. Then, you can see the Glasp icon at the top right. So, please click it.
Step 4: Annotate a PDF
On this screen, you can choose any sentence to annotate. Try to select a sentence. It shows the Glasp pop-up that has a color palette and a couple of icons.
Then, please click on any color you like to annotate. Glasp doesn't define any meaning for each color, but you can define and label it later. By clicking on a color palette, you can annotate the sentence.
If you'd like to take a note, please click the pencil icon on the pop-up. It annotates the sentence and opens a sidebar to take a note. Then, type anything you want and click Enter on the keyboard. It saves your note.
(Optional) Step 5: See all the annotations and notes
Though you can see all the annotations and notes on the sidebar, you can see the whole annotations and notes, and past PDFs on your Glasp profile page. To access it, please click the profile icon at the top right of the sidebar.
You can see all the past annotations on this page. If you'd like to add a category tag, you can type a term in the Tag section.
If you'd like to delete the annotated page, please click the three dots at the top right. It opens a pop-up saying Delete Page, so please delete it there.
Additionally, Glasp has a feature to summarize the PDF. To see how it works, please visit this tutorial.
Also, if you'd like to define and label the meaning of each color, please refer to this page.
What Does Each Highlighting Color Mean?
How to Highlight PDF Files on the Web
FAQs
Q. Can I annotate local PDF files with Glasp?
Currently, Glasp supports web-hosted PDFs. If you want to annotate local PDFs, you can upload them to the web or use Glasp’s local PDF upload feature (see tutorial: How to Upload and Highlight Local PDFs on Glasp).
Q. Are my PDF annotations private?
Yes, by default your annotations are saved to your Glasp profile. For web-hosted PDFs, highlights are visible publicly. For local PDF uploads, highlights are private unless you change visibility settings.
Q. Can I take notes in addition to highlighting?
Yes. Simply click the pencil icon after highlighting a sentence to attach a note. Notes are saved along with your highlights.
Q. Can I export my PDF annotations?
Yes. You can export annotations and notes to popular note-taking tools like Notion, Obsidian, Logseq, Roam Research, or as files in TXT, MD, HTML, CSV, and JSON formats.
Q. Does Glasp allow me to customize highlight colors?
Glasp provides four default colors. While meanings aren’t pre-set, you can define your own system (e.g., yellow = key idea, blue = quotes, pink = research references).
Q. Can I summarize an annotated PDF?
Yes. Glasp has a built-in AI summarization feature for PDFs, helping you turn long documents into concise summaries.
Q. Is Glasp’s PDF annotator free?
Yes. All core PDF annotation features are free to use with Glasp. Some advanced features, like more uploads or extended summaries, may require a premium plan.
Before you leave
If you have any questions, please refer to the FAQ or contact us.
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See you next time,
Glasp team