How to Annotate a PDF for Free: Comments, Notes, Drawing and Text Boxes on Any Device

Knowing how to annotate a PDF saves printing a reading just to write on it. Annotation is everything you add on top of the page without changing the text underneath: comments, sticky notes, freehand drawing, shapes and typed text boxes. The free tools on a Mac, a Windows PC and a phone all do it, but each hides the tools in a different place and saves them differently. This guide gives the steps from Apple, Adobe and Microsoft for each tool, a table for choosing one, a worked example on a short reading, and the pitfalls that lose people's notes.

What you can add when you annotate a PDF

Five kinds of annotation cover almost every reading job. Highlighting is the sixth and has its own guide to highlighting text in a PDF; this page covers the rest.

How to annotate a PDF on a Mac with Preview

Annotations sit on top of the page. The words underneath never change.

Preview cannot edit a PDF's text, but Apple's guide to annotating a PDF in Preview says its markup tools are for giving feedback or writing down something you want to remember.

1. Show the Markup toolbar

   Open the PDF in Preview and click the Show Markup Toolbar button if the toolbar is not showing.

2. Add a note

   Choose the Note tool and type. Apple says you can Control-click a note to change its color and drag it to move it.

3. Add a text box

   Choose the Text tool, type, then drag the box where you want it. Text Style changes the font and color.

4. Draw or add shapes

   Sketch draws a single stroke and replaces it with a standard shape if it recognizes one. Draw, on Macs with a Force Touch trackpad, makes a heavier line when you press harder. Shapes adds boxes, lines and a highlight shape.

5. Save the right way

   Apple says File > Save, File > Export or File > Export to PDF keeps the annotations editable. To flatten them so they cannot be edited, choose File > Print, then Save as PDF.

How to add comments in Adobe Acrobat

Adobe's Acrobat Reader page describes Reader as free and lists comments, sticky notes, highlights, strikethroughs and freehand drawing on desktop and mobile, on Windows, Mac, iOS and Android. Adobe's help page on adding comments with sticky notes gives the steps for Acrobat on the desktop:

1. Select the Add a comment tool from the Quick action toolbar.
2. Select the place in the document where you want the note.
3. Type your comment in the pop-up note that appears.
4. Select Post.

Adobe's help index also has separate pages for text box comments and for shapes, lines and freeform drawings, so the same toolbar is the place to look for those. Save the file when you finish so the comments stay with it.

How to annotate a PDF in Microsoft Edge

On Windows, the browser is often the quickest free option, and Edge has a PDF reader built in. Microsoft's documentation of the PDF reader built into Edge lists three annotation features:

• Inking. Draw on the page for quick notes, a signature or a form. Microsoft says you can change color and stroke width to draw attention to different parts of the file.
• Highlights. Select text, right-click, choose highlights in the menu and pick a color. Microsoft adds that highlights can also be made with a pen or the keyboard.
• Text notes. Select a piece of text, right-click and choose Add Comment. A box opens; type the comment and click the check mark. The text is then highlighted and a comment icon marks the note. Hover over the icon to preview it, or click to edit.

Microsoft lists support for local, online and embedded PDF files. Save the file afterwards so the notes are kept in your copy.

How to annotate a PDF on a phone or tablet

On a phone, the simplest free route is the Acrobat Reader app. Adobe's Reader page says the mobile app runs on iOS and Android and offers the same kinds of marks as the desktop: comments, sticky notes, highlights, strikethroughs and freehand drawing. Adobe adds that the mobile app can also fill and sign forms.

1. Install Acrobat Reader

   Get it from the App Store or Google Play, which Adobe links from its Reader page.

2. Open the PDF in the app

   Open the file from your downloads, an email attachment or a cloud folder, and choose Acrobat Reader as the app.

3. Use the comment tools

   Pick a sticky note, a highlight or the drawing tool, then tap or drag on the page. Zoom in first when you place small marks.

4. Save and check

   Save or share the annotated copy, then open it once more to confirm the marks are there.

Small screens favor short notes and simple marks. For highlight-only work, the phone highlighting guide is shorter.

A worked example: annotating one page of a reading

Suppose page 4 of an assigned PDF contains this sample paragraph, written for the example: "Between 2019 and 2023 the town's bus ridership fell by a third. Officials blamed remote work. Fares, however, rose twice in the same period." Here is a three-minute annotation plan in any of the tools above.

• Comment on the first sentence: "Source for the one-third figure? Check the transit report."
• Draw a circle around "Officials blamed remote work." with an arrow to the margin and a text box: "Claim, no evidence given."
• Sticky note beside "Fares, however, rose twice": "Alternative cause. Use in paragraph 2 of the essay."
• Text box at the top of the page: "Main point: ridership drop has more than one cause."

Four marks, each saying why it is there. A shared shorthand speeds this up; the list of annotation symbols gives one, and the method for annotating any text explains what to look for before you mark. If the notes are checking a claim, annotating sources to verify claims shows how to record what each source says.

Pitfalls when annotating a PDF

• Not saving. Closing a browser tab or a viewer without saving can drop every note. Save, then reopen the file to check.
• Flattening by accident. In Preview, printing to PDF flattens annotations so they can no longer be edited. Keep an editable copy.
• Annotating a scan. If you cannot select text, comment tools tied to a passage will not attach. Use sticky notes, text boxes and drawing instead.
• Assuming every viewer shows every mark. Open the marked file in a second reader before you share it, and fix anything missing.
• Writing marks without reasons. A circle with no note means nothing a week later. Add a word or two to every mark.

Tips for useful PDF annotations

• Read once before you mark. The first pass finds the argument; the second pass marks it.
• One idea per note. Short notes are easier to sort and reply to.
• Keep a key. If circles mean claims and boxes mean evidence, write the key on the first page.
• Gather the notes. Preview's View > Highlights and Notes lists marks in the sidebar, a quick start for writing up.

Annotating a PDF needs no paid software: Preview on a Mac, Edge on Windows and Acrobat Reader on desktop and mobile all add comments, notes, drawing and text. Pick the tool that is already installed, give every mark a reason, and save before you close. For highlighting, phones and web pages, the rest of the guides to highlighting and annotating pick up from here.