How to Annotate a PDF on Computer and Mobile

Summary :

Learn about 4 free and easy methods to annotate a PDF on Windows, Mac, iPhone, iPad, Android, Chrome, etc. Step-by-step tutorials are provided.

Table of Contents

How to Annotate a PDF

How to Annotate a PDF

PDFs are a commonly used file format for documents, books, and even presentations. It can be helpful to annotate a PDF to add notes, highlight important information, or draw attention to key points.

This page covers several practical methods to annotate PDFs on any device, for free and without Adobe Acrobat. All the methods are free and easy, so make sure to give one a try.

👉To save time, download the highly recommended PDF annotator software used in the following tutorial.

How to Annotate a PDF Online for Free

If you’re looking for simple annotation features, then an online PDF annotator is certainly the ideal choice. With it, you can instantly annotate your PDFs on Windows, Mac, iPhone, and Android, without software installation.

The best online PDF annotator service is PDFgear, it’s multi-functional and entirely free to use, there’s no need for registration, and no email address is required.

PDFgear allows you to annotate PDFs, add sticky notes to PDFs, insert images into PDFs, insert fillable text boxes into PDFs, etc.

Step 1. Upload PDF to PDFgear

Go to PDFgear Online PDF Editor, and click the Upload PDF files button to upload the PDF file you need to annotate.

Go to PDFgear Online PDF Annotator

Go to PDFgear Online PDF Annotator

Step 2. Annotate PDF online

Click on the upper-right Add or Edit annotations button, and select the desired markup tool such as text box, highlight, shapes, signature, etc. Meanwhile, you can also insert fillable text boxes into PDFs.

Annotate PDF Online

Annotate PDF Online

Step 3. Download the Annotated PDF

When you’re done annotating, click on the upper-right Download button to download the PDF. After you send the file to others, your annotation will be visible to them.

How to Annotate a PDF Offline

And if you want to annotate a PDF on Windows, Mac, and iPhone offline, and in a more professional way, here I’d like to introduce the best free PDF annotator software.

As one of the best PDF annotators, PDFgear is completely free to use and is packed with tons of practical markup features such as comments, highlights, text boxes, sticky notes, freehand drawings, etc.

Free PDF Annotator Software

Completely free PDF annotator software to highlight PDF, underline text, insert shapes, add text, add sticky notes, insert stamps, etc.

To get started, free download PDFgear on Windows or Mac. Or download the PDFgear app for iPhone and iPad.

Step 1. Launch PDFgear and click the Open File button to open the PDF you need to work with.

Open the PDF File with PDFgear

Open the PDF File with PDFgear

Step 2. From the PDF editing workplace, go to the Comment toolbox for PDF annotations.

Go to Annotate Toolbox

Go to Annotate Toolbox

Step 3. Click on the corresponding buttons to highlight PDF, underline/strikethrough text, insert shapes, add text boxes, sign on PDF, etc.

Step 4. Lastly, click the upper-left Save button to save and export the annotated PDF.

How to Annotate a PDF on Mac in Preview

If you’re a Mac user, there’s another method for you that doesn’t require software installation.

Preview is an inbuilt application on macOS that allows you to do a variety of things with your images and PDF files. In our earlier guide, we’ve introduced how to use Preview to convert PDF to Word without software.

A lot of useful annotation features are provided in Preview’s Markup tool, now let’s take a look.

Step 1. Right-click on the PDF you need to annotate on Mac and open it with Preview.

Step 2. In the selection mode, you can directly select and highlight/underline/strikethrough PDF text.

Highlight PDF on Mac Using Preview

Highlight PDF on Mac Using Preview

Step 3. For more annotating features, click the upper-right Markup button to enter the Preview’s Markup mode.

Enable Preview Markup Tool

Enable Preview Markup Tool

Step 4. From the popup menubar, you’ll find options to select PDF text, copy PDF text from areas, insert shapes, redact text, fill color, etc.

Annotate PDF in Preview

Annotate PDF in Preview

Step 5. When you’re done annotating, go to the File tab and save your PDF.

How to Annotate a PDF in Chrome

Another practical way of annotating PDFs is using the Chrome web browser. Now with the help of additional Chrome browser extensions, you can do a plethora of things with your PDFs, as long as you have installed the right tools.

Chrome extensions are browser-based applications that provide specific functionalities, such as Chrome PDF highlighter extensions.

Here we’ll use the free Chrome PDF editor Kami. With the Kami extension, you can either annotate PDF from Chrome viewing screen or from opening in Google Drive.

Step 1. Download and install Kami from Chrome Web Store.

Get Kami for Chrome

Get Kami for Chrome

Step 2. Open a PDF document from your Google Drive. (You can also drag and drop a PDF into the Chrome browser and access Kami from the Chrome extension menu.)

Open PDF with Kami

Open PDF with Kami

Step 3. From the PDF preview screen, click Open with above, and select Annotate with Kami.

Step 4. Go to Kami’s annotation toolbox to the left to annotate your PDF.

Annotate PDF in Kami

Annotate PDF in Kami

Step 5. From the toolbox, you’ll find options to insert comments, markup text, highlight PDF, and insert shapes.

Different Types of Annotations

PDF annotations, also known as PDF markup, are a set of objects to add to PDF documents. The purpose of annotations is to help users better understand and interpret the content of a PDF file, as well as to collaborate and share feedback with others.

There are many different types of PDF annotations, respectively serving different purposes.

  • Comment
  • Highlight
  • Text box
  • Sticky note
  • Freehand drawing
  • Underline
  • Strikethrough
  • Shapes
  • Stamp

Annotations vs Markups

Markup and annotation are often used interchangeably, but there is a subtle difference between the two terms.

Markup refers to any visual element that is added to a document to indicate a change or modification. This can include anything from adding bold or italicized text, to highlighting text in a different color, to adding symbols or shapes such as checkmarks or arrows.

Annotation, on the other hand, refers specifically to notes, comments, or other explanations that are added to a document to provide additional information or insight. Annotations can be textual or visual, and they can be used to clarify meaning, provide context, or add ideas or opinions.


How do I highlight areas in PDF?

Yes, with PDFgear, you can highlight both text and areas in PDF documents. For area highlights, go to the Annotate toolbox, and select the Area Highlight tool.

Can I draw on a PDF?

Yes. PDFgear allows you to add free drawings into PDF documents. Simply go to the Annotate toolbox and select the Ink tool. Then you’re allowed to draw on PDF using different colors.

How do I add a sticky note to a PDF?

To add a sticky note to a PDF in PDFgear, simply go to the Annotate toolbox, and select the Note tool, it allows you to insert sticky notes with customizable text to any part of the PDF.

Will the annotations be saved after sending the PDF to other people?

If you send the PDF document with the annotations embedded in it, either by attaching it to an email or sharing it through a collaboration platform, then the annotations should be visible.

However, if the recipients use a different PDF viewer or if the annotations are not saved properly, the annotation may be lost.

How to annotate a PDF in OneNote?

You need to create a new page in OneNote, manually copy and paste the text or image from the PDF into OneNote, and use the drawing tools in OneNote to annotate the PDF using pens, highlighters, and a variety of shapes and lines.

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