[2025] How to Annotate PDF in Windows/Mac/iOS/Android: 3 Best Solutions

PDF files are used everywhere, whether in academics, corporations, or government institutes. This has also increased the need to annotate PDFs, like highlighting key points while reading, marking elements to fix while reviewing, or adding sticky notes for more explanation. However, the important question is how to annotate PDF easily and effectively. This is the agenda of this guide. Here, we are going to uncover 3 best solutions to annotate a PDF. So, let's jump right to it!

Part 1. How to Annotate PDF: The Best Tool for Annotation

The best answer to how to make annotations on PDF is to use the best PDF annotator. One such dominating PDF annotation tool in the market is UPDF.

UPDF is a powerful PDF annotator that offers a wide range of annotation functions to markup PDFs the way you want. It offers an all-in-one platform to annotate PDFs while reviewing, collaborating, or sharing feedback.

The key highlights of UPDF PDF annotation functions are as follows:

1. Cross-platform compatibility – Windows, Mac, iOS, and Android
2. 13 markup tools – Highlight, underline, strikethrough, mark, draw, etc.
3. 100+ stickers
4. Manageable comment list (export or delete)
5. 15 default stamps (also supports importing custom images as stamps)
6. Custom signatures
7. Openable attachment
8. 3 sharing options (via links, QR code, or email)

In short, UPDF is a one-stop tool for accessing all possible annotation functions. Don't believe in words. Download UPDF and explore its PDF annotation functions for free yourself.

Part 2. How to Annotate PDF with UPDF for Free

Now that we are clear with the top-notch annotation features UPDF offers, let's head straight to how to annotate PDF with UPDF. To do that, follow the steps as follows:

Step 1. Install UPDF and Open the PDF

Start with downloading and installing UPDF on your devices. Once done, launch the tool and open the PDF by clicking "Open File".

Step 2. Annotate PDF using Four Markup Functions

Now, you can begin annotating the PDF. Click the "Comment" icon from the left sidebar to enter the annotation mode.

Afterward, you can use four functions to markup PDF. These include:

• Highlight
• Strikethrough
• Underline
• Squiggly line

Let's now see how to use all these markup functions:

2.1. How to Annotate PDF with Highlighter

1. Click the "Highlight" option from the top bar.
2. Select the color and drag the highlighter over the text you want to highlight. Once you leave the cursor, the select text will be highlighted.

2.2. How to Make Annotation on PDF with Strikethrough

1. Click the "Strikethrough" option from the top bar.
2. Select the color and drag the strikethrough over the targeted text. Once you leave the cursor, the selected text will be struck through.

2.3. How to Mark Up a PDF with Underline

1. Click the "Underline" option from the top bar.
2. Select the color and drag the underline cursor over the text you want to underline. Once you leave the cursor, the selected text will be underlined.

2.4. How to Annotate PDF with Squiggly Line

1. Click the "Squiggly Line" option from the top bar.
2. Select the color and drag the squiggly line over the targeted text. Once you leave the cursor, the select text will have squiggly lines.

Step 3. Annotate PDF with Comment and Note Functions

UPDF offers four functions to annotate PDFs with comments and notes. These include:

• Sticky note
• Text comment
• Text box
• Text callout

Let's now see how to use all these comment and note functions:

3.1 How to Annotate PDF with Sticky Note

1. Click the "Sticky Note" option from the top bar.
2. Tap where you want to insert the sticky note. Type the text and also change the color if you want.

3.2. How to Make Annotation on PDF with Text Comment

1. Click the "Text Comment" option from the top bar.
2. Tap where you want to insert the text comment. Type the text and customize its properties, like font, style, size, and color.

3.3. How to Mark Up a PDF with Text Box

1. Click the "Text Box" option from the top bar.
2. Tap where you want to insert the text comment. Type the text and customize its properties, like box style and text font, style, size, and color.

3.4. How to Annotate PDF with Text Callout

1. Click the "Text Callout" option from the top bar.
2. Tap where you want to insert the text callout and adjust its position correctly. Once done, type the text and customize its properties, like border color, fill color, text font, etc.

Step 4. Annotate PDF with Pencil to Draw

UPDF offers a pencil function to annotate PDF with drawings. To use it, click the "Pencil" option from the top bar. Specify the pencil color, opacity, and thickness. Once done, you can use it to draw anywhere in the PDF.

You can also use the "Eraser" to erase misdrawn areas.

Step 5. Annotate PDF with Shapes

You can also add different types of shapes to your PDF. To do so, click the "Shape" option from the top bar. Select the shape of your choice and set its other settings. Once done, drag and drop the shape in the PDF at the exact location you want.

Step 6. Annotate PDF with Stamps and Stickers

UPDF offers 100+ stamps and PDF stickers to use for different purposes. For example, you can use the "Reviewed" stamp once you have reviewed the PDF. To access them, click either the "Stamp" or "Sticker" option from the top bar and select and insert the stamp/sticker anywhere you want.

The best thing is that you can also create custom stamps with any shape or content of your choice.

Step 7. Annotate PDF by Attaching File

Another exception annotation feature UPDF offers is the ability to attach files to the PDF. You can attach a wide range of files, such as Word, Excel, PPT, image, or even another PDF.

To access this feature, click the "Attach PDF" option from the top bar. Select the logo you want to present the file with and set its color and opacity.

Now, place the logo anywhere in the PDF you want and then select the file from your PC that you want to attach. Once done, anyone can click the logo and view or download the file.

That's all. So, this is how UPDF answers how to annotate PDF by offering a diverse range of features. You can also follow similar steps to annotate PDF on Mac. In fact, you can also access most of the above features to annotate PDF on iOS or Android devices.

For more detailed steps of how to annotate PDF on Mac, watch the following video:

So, what are you waiting for? It's time for action. Download UPDF and leverage its advanced annotation features to annotate PDF.

Part 3. Other Methods to Annotate PDF

Other than top-notch UPDF, you can also use many other PDF annotator tools. Below we are presenting two other methods to tackle how to mark up a PDF:

1. Annotate with Adobe Acrobat DC

Adobe Acrobat DC also offers many PDF annotation tools. You can highlight, underline, strikethrough, draw, and do much more with Adobe Acrobat DC. Follow the below steps to learn how to make annotations on PDF with Adobe Acrobat DC:

Step 1. Launch Adobe Acrobat DC and open the PDF to annotate.

Step 2. To highlight, underline, or strikethrough, select the relevant option from the small left sidebar. Once selected, annotate the PDF accordingly.

Step 3. To draw or add shape, select the right option from the left sidebar and apply the annotation.

Step 4. Similarly, use other annotation options present in the small left sidebar to annotate PDF the way you want.

This way, Adobe Acrobat also offers a seamless way to annotate PDFs.

2. Annotate with Default PDF Reader (Like Edge PDF Viewer)

You can also annotate PDF with a default PDF reader, like Edge PDF Viewer. It allows you to read the PDF and also access common annotation features. However, it offers limited annotation capabilities, i.e., highlight, draw, and add text boxes.

If you still want to use it, here's how to annotate PDF with Edge PDF Viewer:

Step 1. Open the PDF with the Microsoft Edge browser.

Step 2. To highlight PDF, click the "Highlight" option from the top bar. Adjust the color and thickness and highlight the targeted text.

Step 3. To draw in the PDF, click the "Draw" option from the top bar. Adjust the color and thickness and draw freely on the PDF.

Step 4. To add a text box, click the "Text box" option from the top bar. Tap where you want to add the text box and then type the text.

This way, Edge PDF Viewer's basic-level annotation features let you directly annotate PDF through the web browser.

In addition to the methods mentioned above, other options for annotating PDFs are available, such as the annotation tools in Notability. You can select the one that best suits your specific needs.

Part 4. Which Method Should You Choose to Annotate PDF?

Now that we have discussed three ways to annotate PDFs, the next question is which method to choose. All of them seem to assist in common PDF annotation needs. However, if you look closely, UPDF has an edge over the other two methods.

Some of the reasons why UPDF is dominating are as follows:

• More intuitive, click-based interface.
• 100+ stickers
• Responsive annotation
• Extensive markup utilities
• Various stamps
• Cost-friendly plans

Although Adobe Acrobat DC does seem to give UPDF competition, UPDF outclasses it with a more user-friendly interface, support for adding stickers, and highly cost-friendly plans. For instance, UPDF Pro costs $32.99/year or $52.99/one-time, while Acrobat costs $155/year.

Furthermore, UPDF is more than a PDF annotator. With UPDF, you can also edit, convert, compress, merge, organize, OCR, and protect PDFs. Furthermore, it offers a PDF AI assistant (UPDF AI) to get AI-powered PDF summaries, translations, and explanations.

Conclusion

Many PDF tools can tackle "how to annotate PDF". However, only a few of them really offer the features for the best PDF annotation experience. From the above discussion, it is evident that UPDF is one such best PDF annotation tool. It offers all the basic to advanced annotation features users need to annotate PDFs. On top of that, its intuitive interface and cost-friendly plans make it shine as the ideal tool to annotate PDFs. Therefore, download UPDF now and have the best experience annotating PDFs.