To highlight text in PDF for free, open the PDF in a free PDF reader or free online PDF editor, select the words you want to mark, and choose the highlight tool. The words will be covered with a coloured background, usually yellow, so they stand out when you read the document again. You do not need paid software for this, and the same basic method works on mobile and PC.
Highlighting is useful for study and notes because it helps you find key points quickly later. Instead of reading a whole document again, you can scan for the marked passages, definitions, and conclusions. It also helps when you share a document with a classmate or colleague, because the important parts are easy to spot. The key is to highlight sparingly, so the marks still mean something when you return to the file.

How to Highlight Text in PDF for Free on Any Device
Most free PDF tools follow the same steps, whether you use a browser, a phone app, or a desktop program. Start with a copy of the PDF, so the original stays clean if you change your mind.
- Open the PDF in a free PDF reader or free online PDF editor that offers a highlight or annotation tool.
- Find the highlight tool in the toolbar. It is often shown as a marker pen icon, or listed under comments and annotations.
- Select the text you want to highlight by dragging across it with your mouse or finger. The highlight colour is usually yellow by default.
- If the tool allows it, choose a different colour for a different kind of note. For example, use yellow for key ideas and another colour for questions.
- Save the file as a new PDF, or download the highlighted version. Then open the saved file and check that the highlights are in the right places.
If you cannot select the text, the PDF may be a scanned image rather than real text. In that case, highlighting will not work until the file has a text layer. Some free tools offer text recognition, but for a simple scan it is often easier to add a note or a coloured shape over the page, or to use a scanned copy that has been converted with text recognition.
How to Highlight Text in PDF on a PC
On a computer, highlighting is usually easiest with a mouse, because you can select long passages accurately and check the result on a large screen. Open the PDF in your browser or in a free desktop PDF reader, and look for the highlight tool before you start selecting text.
- Open the PDF and zoom in until the text is comfortable to read.
- Select the highlight tool, then drag across the first passage you want to mark.
- Repeat for other passages, changing colour only when it helps you tell different types of notes apart.
- Use the tool’s comment or note option if you want to explain why a passage matters, rather than relying on colour alone.
- Save the highlighted PDF under a new name, such as the original name plus “highlighted”, so you can tell it apart from the clean copy.
On a PC, it is also easier to remove a highlight if you mark the wrong words. Select the highlighted text again and choose the remove or delete highlight option, or use undo straight after the mistake. Check the whole page before you save, because a highlight that starts or ends in the wrong place can change the meaning of a sentence.
How to Highlight Text in PDF on Mobile
To highlight text in PDF on a phone, use a free PDF reader app or a free online PDF editor in your mobile browser. The steps are the same, but selection is done with your finger, so zooming in first makes a real difference.
- Open the PDF from your phone storage, files app, or cloud drive.
- Tap the highlight or annotation tool in the app toolbar.
- Press and drag across the text you want to highlight, and adjust the selection handles if the first selection is too short or too long.
- Choose a colour if the app offers one, and repeat for other passages.
- Save or export the highlighted PDF, then open the saved file to confirm the highlights stayed in place.
On a small screen, it helps to highlight in short sessions and to check each page before moving on. Long selections are easy to get wrong on a phone, and fixing them later takes longer than selecting carefully at first. If you need to highlight a long document, a computer is usually faster, but a phone is ideal for quick reading notes on the go.
Tips for Clear, Useful Highlights
- Highlight only the main idea in each paragraph, not the whole paragraph. A page covered in colour is no easier to read than an unmarked page.
- Use a simple colour system and stick to it. For example, one colour for definitions, one for examples, and one for things to check later.
- Add a short note next to a highlight when the reason for marking it is not obvious. A note will save you from wondering later why you marked a passage.
- Keep a clean copy of the PDF. If your highlights become messy, you can start again without losing the document.
- Check the highlighted file on the device where you will read it, such as your phone, before you rely on it for study or revision.
Common Mistakes to Avoid When You Highlight Text in PDF
One common mistake is highlighting too much. When everything is marked, nothing stands out, and revision takes just as long as reading the document again. Another mistake is highlighting before you understand the passage. Read a paragraph first, decide what matters, and then mark only that part.
Other mistakes are easy to avoid once you know them. Do not overwrite the only copy of a PDF, because a bad highlight or a lost file is then hard to undo. Do not use so many colours that you need a key to read your own notes. And do not skip the final check: open the saved PDF and confirm the highlights are on the right words, especially if you plan to share the file with someone else.
Frequently Asked Questions
Can I highlight text in a PDF for free?
Yes. Free PDF readers, free desktop programs, and free online PDF editors all offer a highlight tool for most PDFs with real text. You do not need to pay to mark passages for study or notes.
Why can I not select text to highlight in my PDF?
Your PDF is probably a scanned image, not a text document. Highlighting needs selectable text, so a scanned page will not respond to selection. Look for a tool with text recognition, or add a note or shape over the page instead.
Will my highlights stay when I share the PDF?
They should, if you save or download the highlighted file as a new PDF and share that file. Do not share a screenshot of the highlights, and do not share the original unmarked file by mistake. Open the saved file first to confirm the highlights are there.
Can I remove a highlight from a PDF?
Yes, in most tools. Select the highlighted text again and choose the remove highlight option, or use undo if you have just made the mark. Save the file again after removing it, and check that the text underneath is still clear.
In short, to highlight text in PDF for free, open the file in a free reader or editor, select the key passages, choose a colour, and save a new copy. Highlight sparingly, add notes where they help, and check the saved file before you share it.


















