How to Annotate PDF: Easy Steps to Add Notes, Highlights & More

PDF annotation lets you highlight text, add comments, write notes, draw on pages, and mark important information without changing the original document content.

The best way to annotate a PDF depends on what you need to mark and where you are working. Desktop PDF editors offer the widest range of tools, while online and built-in apps can be more convenient for quick annotations.

Below, we'll cover the main ways to annotate a PDF, what each annotation tool is best for, and how to choose the right method.

Part 1. Which PDF Annotation Tool Should You Use?

PDF annotation tools serve different purposes. Use highlights and underlines to emphasize text, comments to explain a change, and shapes or drawings to point to a specific area. Choosing the right tool keeps the document clear and makes feedback easier to understand.

What you want to do	Annotation tool	Example
Emphasize important text	Highlight	Mark a key definition or finding
Draw attention without highlighting	Underline	Emphasize a sentence or clause
Suggest deleting content	Strikethrough	Mark outdated or unnecessary text
Ask a question or explain a change	Sticky note or comment	Add feedback without covering the page
Add visible words to the page	Text box	Insert a label or short instruction
Point to an exact area	Arrow, shape, or callout	Identify an issue in a chart or image
Add handwritten feedback	Pencil or drawing tool	Circle an item or sketch a correction
Show document status	Stamp	Mark a file as Approved or Reviewed

In the PDF above, reviewers have marked important scientific sentences, so they clearly stand out from the surrounding text. Key terms are underlined to guide readers toward concepts they should easily remember during later study sessions. Several lines are highlighted in yellow, helping users quickly spot the main explanation without rereading the whole page.

A small comment saying “Remove this part” points to the sentence that should be deleted in the next revision. Near the bottom, an approval stamp and other notes record that someone has already reviewed and accepted these changes.

Here you can check the chart below to choose the PDF annotator for your needs after knowing the usage of different annotation tools, then which kind of annotators you need is easy to choose in the following chart.

Tool	Platform	Price	Key Annotation Features	Best For
Microsoft Edge	Windows	Free (built-in)	Highlight, draw, add text	Quick, no-install markups
macOS Preview	Mac	Free (built-in)	Highlight, notes, shapes, signatures	Mac users
Google Drive	Web, Android, iOS	Free	Highlight, comment, draw	Google Drive users
Files app (iOS)	iPhone, iPad	Free (built-in)	Markup, signatures	Apple mobile users
UPDF	Win, Mac, iOS, Android	Paid ($49.99 per year or $79.99 for lifetime license)	Full annotation + AI summary	Cross-platform professionals
Adobe Acrobat	Win, Mac	Paid (~$240 per year)	Full annotation + OCR	Enterprise users
PDFgear	Win, Mac, iOS, Web	Free	Highlight, underline, shapes	Budget-conscious users

Then let's see how to annotate PDF step by step and in different devices.

Part 2. How to Annotate a PDF in 5 Simple Steps

No matter which app or device you use, the basic annotation steps stay similar. Look at the steps below:

1. Open or Upload the PDF

Open the PDF in a desktop PDF editor, a browser-based PDF viewer, or an online annotation tool. If you are working with confidential material, use a local desktop application instead of uploading the file to an online service.

2. Open the Annotate, Comment, or Markup Toolbar

Look for a toolbar labeled Annotate, Comment, Markup, or Draw. The exact name varies by application, but these menus normally contain highlights, notes, text boxes, shapes, and drawing tools. In UPDF, this is done by Comment Mode, in Edge, this is from Draw”

3. Choose and Apply an Annotation

Select the text or area you want to mark. Use Highlight, Underline, or Strikethrough for selectable text. Use a sticky note, text box, arrow, shape, or pencil tool when you need to add feedback to a specific area of the page.

4. Review and Manage the Annotations

Check that each annotation is easy to understand. Edit its color, position, author name, or comment text when needed. Delete duplicated marks and avoid highlighting entire paragraphs unless every sentence is relevant.

5. Save, Export, or Share the PDF

Save a separate copy so the original PDF remains unchanged. Before sharing, reopen the file in another PDF reader to confirm that the annotations are visible. Flatten the annotations only when you want to make them difficult to edit or remove.

These basic steps apply whether you annotate PDF files on Windows, macOS, mobile, or the web, and whether you are a student, researcher, or part of a business team.

Part 3. How to Annotate a PDF on Different Devices

Cross‑device annotation keeps your notes and feedback consistent wherever you open the same document. It helps users move between your laptop and phone without losing important markings. Now, we will look at how each type of device supports different PDF annotation needs.

Device or method	Best for	Main limitation
Desktop PDF editor	Detailed review and many annotations	Requires installation
Preview on Mac	Free built-in Mac annotation	Not a full PDF text editor
Chrome or Edge	Quick local markup	Limited review features
Mobile app	Notes and approvals on the go	Smaller screen
Online annotator	One-time tasks without installation	Upload, privacy, or usage limits

How to Annotate a PDF on Windows

On Windows, open the PDF in professional PDF annotator like UPDF for a complete annotation workflow or use Microsoft Edge for quick text, drawing, and markup tasks. For detailed steps covering multiple Windows tools, see our guide to annotating PDFs on Windows.

Open PDF file in Edge and then you can click the Draw/Highlight in the toolbar, choose color and customize the thickness, then you can save the changes.

On Linux, annotation helps researchers and other professionals organize technical specifications, marking requirements, constraints, and implementation notes with annotate PDF Linux. It suits reviewers who open reference PDFs alongside main documents while checking consistency between sections.

For a professional PDF editor, take UPDF as an example: Open PDF file from upload or drag in Home interface, then click Tools to enter Comment Mode, choose the annotation tools to markup file, finally click save on the right corner.

Here you can check the video guide.

How to Annotate a PDF on Mac with Preview

Annotating a PDF on Mac works well when professionals analyze detailed reports or structured presentations.

1. Open the PDF in Preview.
2. Click Show Markup Toolbar if the tools are hidden.
3. Select Highlight, Text, Note, Shape, Draw, or Sign.
4. Add the annotation and move or format it as needed.
5. Choose File > Save or Export to keep annotations editable.

How to Annotate a PDF in Google Chrome

The steps to annotate a PDF in Chrome are simple and easy,

1. Open the PDF in Chrome, preferably in a new tab.
2. Select Draw.
3. Choose the pen or highlighter.
4. Select a color and line size, then mark the PDF.
5. Click Download and choose With your changes.

Chrome is useful for quick highlighting, drawing, and signatures, but it does not provide the same range of review and comment-management tools as a full PDF editor.

How to Annotate a PDF on iPhone, iPad, or Android

Office managers and other professionals annotate a PDF on Android or iOS when they are away from their desks. Phones are handy for highlighting single lines that need attention before a call or quick discussion. They often add very short comments to clarify numbers, correct wording, or remind themselves about follow‑up.

Option 1: Use Apple Markup on iPhone or iPad (Free, Built‑In)

Apple's Markup tool works inside the Files app, Mail, Books, and other apps that can open a PDF. It is the fastest way to draw, highlight, add text, or sign a PDF without installing anything.

1. Open the PDF in the Files app (or tap a PDF attachment in Mail).
2. Tap the Markup button (the pen‑tip icon) to show the drawing toolbar.
3. Choose a pen, highlighter, or pencil, then adjust the color and line thickness.
4. To add typed text or a signature, tap the Add (+) button and select Text or Signature.
5. Tap Done to save the changes to the file.

Finger vs. Apple Pencil: You can annotate with your finger on any iPhone or iPad, which is fine for short marks and signatures. On a supported iPad, an Apple Pencil gives you finer control for handwriting, precise underlines, and detailed drawings, and lets you rest your palm on the screen while writing. If you annotate PDFs regularly on an iPad, a stylus is worth using.

Option 2: Use Google Drive on Android (Free, Built‑In)

Android does not include a system‑wide markup tool like Apple Markup, but the Google Drive app provides a basic, free annotation option on most Android devices.

1. Open the Google Drive app and locate the PDF.
2. Tap the PDF to open it.
3. Tap the pen icon in the bottom‑right corner.
4. Choose a highlighter, pen, or add text.
5. Annotate the PDF with your finger or stylus.
6. Tap Save or the checkmark to save changes.

Option 3: Use a Dedicated PDF App - UPDF for Full Annotation Features

Use a dedicated PDF app when you need highlights tied to selected text, sticky notes, text boxes, shapes, stamps, and a way to review all annotations in one place. These apps work on both iOS and Android.

1. Open the PDF in your chosen app (for example, UPDF).
2. Tap the annotation or markup tool in the toolbar.
3. Select text to apply Highlight, Underline, or Strikethrough, or tap the page to add a Sticky Note, Text Box, or Shape.
4. Use the pencil tool for handwritten notes — with your finger, an Apple Pencil, or a stylus.
5. Save the file, or sync it through cloud storage to continue reviewing on your desktop.

Save, Sync, and Share from a Mobile Device – What to Check

Before you send an annotated PDF from your phone or tablet, check these three things to avoid surprises:

• Save a copy. Some mobile apps write annotations directly into the original file. If you need a clean version, duplicate the PDF before you start marking it up.
• Sync across devices. Store the PDF in a cloud service (or use an app with its own sync) so annotations added on your phone appear when you reopen the file on your computer.
• Check before sharing. Open the annotated PDF in a different PDF reader, or on another device, to confirm the highlights and comments are visible to recipients. If compatibility matters, share a flattened copy.

How to Annotate a PDF Online for Free

Browser‑based tools support article markups similar to how to annotate an article online. Real‑time updates reduce delays because teammates immediately see each new note, reply, or change request together.

1. Open an online PDF annotator in your browser.
2. Upload the PDF from your device or cloud storage.
3. Select a highlight, text, note, shape, or drawing tool.
4. Add the required annotations.
5. Download the annotated PDF and reopen it to check the result.

Best Practices for Effective PDF Annotation

Read the relevant section once before adding annotations. This reduces unnecessary highlights and helps you identify the main argument or action item.

1: Create a Consistent Color-Coding System

Researchers and lawyers like color systems as they show meaning at a glance. Use yellow for key concepts, blue for references, and green for supporting examples. Remember to keep your colors simple to make every document feel organized.

Yellow	Key concepts / main arguments
Green	Supporting evidence / examples
Red	Errors / contradictions / issues
Blue	Definitions / terminology
Orange	Questions / unclear points

Rule of thumb: Use no more than 4‑5 colors per document. Too many colors = no meaningful signal.

2: Use Annotations as Part of a Workflow

Students might highlight and turn notes into exam study cards. Researchers can mark methods and gaps, then export notes into literature matrices. Moreover, legal and business teams can flag risks and track decisions directly inside documents.

5‑Step Annotation Workflow Checklist

1. First read: Read the PDF once without marking anything. Understand the big picture.
2. Second read: Highlight only key ideas, main arguments, or important data. (Resist the urge to highlight everything!)
3. Add context: Write short notes or questions in comments for anything important, unclear, or surprising.
4. Connect ideas: Look for patterns, recurring themes, or relationships. Use shapes/arrows to show connections.
5. Review & export: Review your annotations. Decide what to keep, what to remove, and how to use them for your next task (study, write, present, approve).

3: Common Annotation Mistakes to Avoid

• Excessive highlighting makes everything look important, and nothing actually helps later.
• Using too many colors confuses readers and hides your main message or structure.
• Writing long notes and mixing personal and team comments creates clutter and misunderstandings.

Together, these habits help you annotate clearly instead of cluttering your PDFs with confusing marks. In the next section, we will see how real users apply these practices in everyday study, research, legal, and business scenarios.

Common PDF Annotation Use Cases

Users utilize annotations in different ways, based on their daily documents and decisions. A textbook, a legal contract, or a project brief all need their own clear annotation approach. Let’s explore how real‑world roles turn PDF markups into smoother study, review, and approval workflows together.

Use case	What to annotate	Recommended tools	Output
Study and exam preparation	Definitions, arguments, questions	Highlight, note, drawing	Revision notes
Research papers	Claims, methods, evidence, citations	Highlight, comment, tag	Literature review notes
Contract review	Risks, unclear clauses, proposed deletions	Highlight, comment, strikethrough	Reviewed contract draft
Teaching and grading	Errors, strengths, next steps	Callout, stamp, drawing	Actionable student feedback
Team review	Changes, questions, approvals	Comments, replies, stamps	Consolidated review file

Students use annotations to manage heavy readings and find key ideas faster, whether they are working with printed PDFs or Kindle book annotations.

Researchers use annotations to understand papers, connect sources, and turn many articles into a clear literature review.

Lawyers review complex contracts and need a clear way to track every change. Next, we will see how to annotate PDF files with a PDF annotator to make this work easier:

With heavy marking loads, teachers rely on quick annotations to review work and give students clear feedback.

In busy teams, shared PDF comments keep projects moving, so everyone understands decisions without long meetings. Many proposal documents sit in shared folders, so teammates often need to annotate PDFs in Google Drive during review.

Knowledge 1. What Is PDF Annotation?

PDF annotation means adding a review layer to a PDF without replacing its original content. Annotations can include highlights, underlines, strikethroughs, comments, text boxes, drawings, shapes, stamps, and signatures. They are commonly used to record notes, suggest revisions, explain issues, and collect feedback.

Annotation is different from PDF editing. Annotation adds marks or comments on top of the document, while editing changes the underlying text, images, links, or page content.

Knowledge 2. PDF Annotation Limitations and Problems

Scanned PDFs

You can usually place annotations on scanned PDFs, but selecting or editing the scanned text may require OCR.

Password-Protected PDFs

Document permissions may restrict some annotation actions.

Annotation Compatibility

Different PDF viewers may display or handle certain annotation types differently.

Flattened Annotations

Flattening can merge annotations into the document content, which may prevent users from editing those annotations later.

Printing

Not every interactive annotation behaves exactly the same way on paper as it does on screen.

When to Save, Share, or Flatten an Annotated PDF

Here you can check when to use save/save as or flatten after annotating PDF, and can annotations still be edited or not.

Method	Use it when	Can annotations still be edited?
Save or Save As	You want to continue reviewing later	Usually yes
Share for review	Multiple people need to comment	Depends on the review platform
Flatten and export	The marks should remain fixed	Usually no

• Save an editable working copy.
• Close and reopen the file to confirm the annotations were saved.
• Open it in a second PDF reader to check compatibility.
• Share the editable copy when collaborators need to reply or revise comments.
• Create a flattened copy only for final distribution or printing.

FAQs

Conclusion

To conclude, strong annotation habits turn dense PDFs into useful resources for everyday work. Now this article has shown how to annotate PDF files with better tools and fewer mistakes.

With the right methods, annotations support faster reading and smoother collaboration across document types. If you are ready to put this into practice, pick one PDF you use today and apply these annotation techniques from start to finish in UPDF.