How to Highlight in a PDF: 4 Free Ways (Online, Mac, Windows)

To highlight in a PDF, open it in a PDF tool that has a highlighter, pick the Highlight tool, and drag across the text you want to mark, then save the file. You can do it for free in your browser with the WoowPDF PDF Annotator, or with apps you may already have: Adobe Acrobat Reader, Preview on a Mac, or Microsoft Edge on Windows.

Below are the steps for each, plus how to change the colour, remove a highlight, and what to do when the text will not highlight.

Which way to highlight a PDF should you use?

Use the browser tool if you want nothing to install and nothing uploaded, Preview if you are on a Mac, and Edge or Acrobat Reader if you are on Windows. All four save real PDF highlights that other readers can see.

Method	Cost	Works on	Highlight colours	Good for
WoowPDF PDF Annotator	Free, no sign up	Any browser, desktop or phone	Any colour, adjustable opacity	Quick marking with no install, private files
Adobe Acrobat Reader	Free app	Windows, Mac, mobile	Any colour	People who already use Acrobat
Preview	Built in	Mac	Several preset colours	Mac users
Microsoft Edge	Built in	Windows, Mac	Several preset colours	Windows users with Edge as PDF reader

How to highlight in a PDF online (free, no upload)

The PDF Annotator highlights text in your browser: the file is opened and saved on your device and never sent to a server.

1. Open the PDF Annotator and drop your PDF on the page, or click Choose file.
2. The Highlight tool is selected when the file opens. Set the colour and opacity in the toolbar if you want something other than yellow at 45 percent.
3. Drag from the first word to the last word you want to mark. The highlight snaps to each line of text in between and stops at the characters you chose.
4. To fix a mistake, press Undo, or switch to Select, click the highlight and delete it.
5. Choose how to save: editable annotations (others can see, change or delete the highlights in any PDF reader) or flattened (painted into the page so they cannot be removed). Press Save annotated PDF and download the file.

The same toolbar also has underline, strike out, sticky note comments, a pen and shapes, so you can mark up a whole document in one pass.

How to highlight a PDF in Adobe Acrobat Reader

In the free Acrobat Reader, select the highlighter in the toolbar, then drag across the text. The steps are short:

1. Open the PDF in Acrobat Reader.
2. Click the Highlight text tool (the marker icon) in the toolbar. In some versions it sits under Comment or All tools.
3. Drag across the text.
4. To change the colour, click the highlight and pick a new colour from the small menu that appears, or use its properties.
5. Save with Ctrl+S (Windows) or Cmd+S (Mac).

How to highlight a PDF on a Mac with Preview

Preview has a highlight button in its toolbar, so no extra app is needed.

1. Open the PDF in Preview.
2. Click the Highlight button (a marker with a line under it) in the toolbar. Click the small arrow next to it to choose a colour, or underline and strike through.
3. Drag across the text. Every selection you make while the button is on gets highlighted.
4. Click the button again to turn highlighting off, then save with Cmd+S.

To remove a highlight in Preview, Control-click it and choose Remove Highlight.

How to highlight a PDF in Microsoft Edge

Edge opens PDFs by default on Windows and has a built in highlighter.

1. Open the PDF in Edge (right click the file, Open with, Microsoft Edge).
2. Select the text, right click it and choose Highlight, then a colour. Or click Highlight in the PDF toolbar and drag over the text.
3. Press Ctrl+S to save the highlights into the file. If you close the tab without saving, they are lost.

How to remove or change a highlight in a PDF

To remove a highlight, click it and press Delete, or right click it and choose Delete (Acrobat, Edge) or Remove Highlight (Preview). In the PDF Annotator, switch to Select, click the highlight and press the trash button or the Delete key.

This only works while the highlights are editable annotations. If the file was saved flattened, or printed to PDF, the yellow is part of the page image, and the only clean way back is the original file. Keep an unmarked copy when you highlight something important.

Why can't I highlight text in my PDF?

Usually the PDF has no real text (it is a scan or a photo), or its security settings block comments.

Problem	Why it happens	Fix
The highlighter draws a box, not lines of text	The page is a scanned image with no text layer	Run PDF OCR first, then highlight; highlights will then snap to the words
Highlight tool is greyed out	The PDF has a permissions password that blocks commenting	If you own the file, remove the restriction with Remove PDF Password
The highlight covers the wrong text	Text is stored out of order in the file (common in multi column layouts)	Highlight one column at a time, or drag a box over the area
Highlights vanish in another app	They were not saved, or the other app hides comments	Save before closing; turn on comments or annotations in the other app
Highlights print grey or not at all	Print settings exclude comments	In the print dialog, choose to print the document and markups, or save a flattened copy

On a scan, the PDF Annotator still lets you mark the area: drag a box over the lines and it is highlighted as a block.

Is a highlight the same as hiding text?

No. A highlight or a black box drawn over text leaves the text in the file, where anyone can copy it or remove the mark. To hide names, numbers or account details for good, use Redact PDF, which deletes the text under the box.

Tips for highlighting PDFs well

• Use colours with a meaning. For example yellow for key points, green for definitions, pink for questions. Pick lower opacity for dark colours so the text stays readable.
• Highlight phrases, not paragraphs. If everything is yellow, nothing stands out.
• Add a comment to explain why. A sticky note next to a highlight tells a reviewer what to change.
• Flatten the final copy you send to someone who must not edit the marks; keep the editable version for yourself.
• Need to change the words themselves? Highlighting does not edit text. Use Edit PDF for that.

Ready to mark up your file? Open the free PDF Annotator, drop the PDF and start highlighting: no account, no watermark, and the document never leaves your device.

Frequently asked questions

How do I highlight text in a PDF for free?

Open the PDF in a free tool with a highlighter, such as the WoowPDF PDF Annotator in your browser, Adobe Acrobat Reader, Preview on a Mac or Microsoft Edge. Choose Highlight, drag across the text and save the file.

Why won't my PDF let me highlight?

The PDF is probably a scanned image with no text layer, or it has security settings that block comments. Run OCR on a scan to add a text layer, or remove the restriction if you own the file.

Can I highlight a PDF on my phone?

Yes. The PDF Annotator works in mobile browsers, so you can open the PDF, drag a finger across the text and save. Acrobat Reader's mobile app can highlight too.

How do I change the highlight colour in a PDF?

Select the colour before you highlight, or click an existing highlight and choose a new colour. In the PDF Annotator, the colour and opacity are set in the toolbar.

Will other people see my PDF highlights?

Yes, if you save them as annotations: Acrobat, Preview, Edge, Chrome and Firefox all show standard PDF highlights. If you flatten them, they become part of the page and show everywhere, but can no longer be removed.