How to Highlight in a PDF (Free, No Adobe Needed)

The quickest free way to highlight a PDF is the FileNaut PDF Editor: open the file, pick Highlight Pen, drag across the words you want to mark, and click Save PDF. It runs in your browser, so the document is never uploaded, and it works on scanned pages where ordinary text highlighters do nothing.

If you already have a PDF reader, you can also highlight there. Mac Preview, Adobe Acrobat Reader and Microsoft Edge all do it for free. The methods are not interchangeable, though. Some create a highlight you can click and delete later; others paint the colour into the page for good. That difference decides which one to use, and it is the reason "how do I remove this highlight?" is nearly as common a question as how to add one. Both are covered below.

We tested the browser method on real files and checked the saved PDFs: where each highlight lands, whether the text underneath can still be searched and copied, and what happens to highlights a PDF already had.

Best for: anyone without a PDF app, scanned documents, Chromebooks, phones, and files you would rather not upload. There are two highlighters, one for lines of text and one for areas.

Highlight Pen: for lines of text

1. Open the PDF Editor and drop your PDF onto the page, or click Browse Files.
2. Go to the page you want. Click a thumbnail on the left, or use the arrows at the top.
3. In the tools panel, under Shapes & Redact, click Highlight Pen. (On a phone, it is HL Pen in the bottom toolbar.)
4. Press at the start of the text and drag to the end. When you let go, the stroke snaps to a straight horizontal line between where you started and where you stopped, so a slightly wobbly drag still gives a neat highlight.
5. Repeat for each line. Each stroke is a separate item you can select, drag into place, or remove.
6. Click Save PDF. The highlighted copy downloads as edited_ followed by your file name.

The pen starts yellow, 16 pixels thick and 40% opaque, which lets the text show through. In the options panel you can pick one of five colours (yellow, green, blue, pink, orange) or any custom colour, set the width from 1 to 40, and set the opacity from 10% to 100%. If the pen covers only part of the letters, raise the width to match the text size.

Highlight Box: for paragraphs, tables and images

1. Click Highlight Box (HL on a phone) and pick a colour.
2. Click on the page where the top-left corner of the box should go.
3. Drag the box to adjust it, and use the arrow buttons above it to make it wider, narrower, taller or shorter until it covers the area.
4. Click Save PDF.

The box is saved at 40% opacity, like a translucent sticky flag over the area. It is the better choice when you want to mark a whole block, such as a clause in a contract or a row in a table, rather than line by line.

Changing the colour afterwards: click a highlight to select it, then pick a new colour in the options panel. It changes only the selected highlight. Mistakes: the pen panel has Undo, Redo and Clear Page, and every item has a × to delete it before you save.

A PDF can hold a highlight in two very different ways, and most guides never mention it.

• Annotation highlights. Preview, Acrobat Reader and Edge add the highlight as a separate note layered on top of the page. You can click it later, change it, add a comment to it or delete it, and anyone with a PDF reader can do the same.
• Flattened highlights. The FileNaut editor draws the colour onto the page itself, the way a stamp or a signature is added. It looks the same in every viewer and cannot be accidentally clicked away, but it also cannot be removed by the next person who opens the file.

We checked the saved files to be sure what that means in practice:

One more thing we tested: if your PDF already has annotation highlights, the FileNaut editor keeps them. A file with an existing Acrobat-style highlight came out of the editor with that highlight still present as a deletable annotation, alongside the new one.

Rule of thumb: highlighting a document you are sending for review, where the other person should be able to clear your marks? Use an annotation highlight. Marking a copy for yourself, a scan, or a file that must look identical for everyone? Flattened is fine, as long as you keep the unmarked original.

Preview comes with every Mac and makes annotation highlights.

1. Open the PDF in Preview. It is the default for PDFs; if another app opens instead, right-click the file and choose Open With → Preview.
2. Click the Highlight button in the toolbar (a marker pen icon). The small arrow next to it chooses the colour, and also offers underline and strikethrough.
3. Drag across the text. With the highlighter switched on, every selection you make is highlighted straight away.
4. Click the Highlight button again to switch it off, then save with File → Save (or Export as PDF to keep the original untouched).

To remove a highlight in Preview: right-click (or Control-click) the highlighted text and choose Remove Highlight.

Preview's highlighter follows the text, so it does nothing on a scanned page where the words are just a picture. Use the Highlight Pen in Method 1 for those. Menu names can shift a little between macOS versions; if the button is missing, look under Tools → Annotate.

The free Acrobat Reader app can highlight; you do not need a paid Acrobat subscription for it.

1. Open the PDF in Acrobat Reader.
2. Select the text you want to highlight. A small toolbar appears next to the selection.
3. Click the highlight icon in that toolbar. Alternatively, choose the highlighter from the comment tools and drag across as many passages as you like.
4. Save the file.

To change the colour, click the highlight and choose a colour from the options that appear, or right-click it and open its properties. To remove it, click the highlight and press Delete, or right-click and choose Delete. To clear many at once, open the Comments list, select the highlights there, and delete them together.

Adobe redesigns Reader's toolbars fairly often, so the icons may sit in a slightly different place in your version, but select-text-then-highlight has been the pattern for years.

If you are on Windows, the browser you already have may be enough. Open the PDF in Microsoft Edge (drag the file into an Edge window, or right-click it and choose Open with → Microsoft Edge), select the text, and choose Highlight from the menu that appears, where you can also pick a colour. Save with the save icon or Ctrl+S.

Google Chrome's built-in PDF viewer has been gaining annotation tools, but what you get depends on your Chrome version and operating system. If your viewer shows a pen or annotation icon in its toolbar, you can draw a highlight with it; if it does not, your version cannot highlight, and the PDF Editor works in any version of Chrome instead.

How you remove a highlight depends on which of the two kinds it is.

If you can click it and it gets selected, it is an annotation, and removing it is easy:

• Preview (Mac): right-click the highlighted text and choose Remove Highlight.
• Acrobat Reader: click the highlight and press Delete. To remove all of them, open the Comments list, select everything, and delete.
• Edge: click the highlight and choose to remove it from the menu that appears.

To remove every highlight from a long document at once, a few lines of Python with the free pypdf library will do it. We ran this exact script on a test file: it removed the highlight and left a sticky-note comment on the same page, and all of the text, untouched:

from pypdf import PdfWriter

writer = PdfWriter(clone_from="input.pdf")
writer.remove_annotations(subtypes="/Highlight")
writer.write("no-highlights.pdf")

Install the library with pip install pypdf first. Leave out subtypes=... and it removes every annotation, including comments and sticky notes, which is usually not what you want.

If clicking it selects nothing, the highlight is part of the page: it was flattened by an editor like FileNaut's, the file was "printed to PDF" after highlighting, or it is a scan of paper that was marked with a real highlighter. No reader can delete it, because there is no separate object to delete. Your options, in order:

1. Go back to the original, unhighlighted file. This is why it is worth keeping one.
2. Ask whoever sent it for a clean copy.
3. If you only need the words, copy the text out. The text layer is still there under a flattened digital highlight, and PDF OCR can read the words from a scan.

Do not try to cover a flattened highlight with a white box. That hides the words underneath as well.

If the highlighter in your reader does nothing, it is almost always one of three things.

• It is a scan. The page is a photo of text, so there are no words to select, and select-to-highlight tools have nothing to grab. Quick test: try to select a single word. If you get a box around the whole page, or nothing at all, it is a scan. Use the Highlight Pen or Highlight Box in the PDF Editor, which draw wherever you drag.
• The PDF is restricted. Some PDFs have a permissions setting that blocks comments and changes even though they open without a password. Readers grey out the highlight tools, and the FileNaut editor shows a message when you try to save. If you are entitled to edit the file, run it through Unlock PDF first. In our test, a file that opened freely but blocked editing came out unrestricted and then highlighted and saved normally. If the PDF asks for a password to open it, you need that password.
• You are in the wrong mode. Many readers highlight only while the highlighter is switched on, or only after you select text. Select a word first, then look for the highlight option in the menu that appears.

• Highlight less. If half the page is yellow, nothing stands out. Mark the phrase that matters, not the whole paragraph.
• Give colours a meaning, and say what it is. For example, yellow for key points, green for "agreed" and pink for "needs a decision".
• Keep the opacity low. Around 40% keeps the text readable, on screen and in print. At 100% the pen becomes a solid bar that hides the words.
• Match the pen to the text. For normal body text, a width of about 14 to 20 covers the line without spilling onto the lines above and below.
• Keep an unmarked original. Save the highlighted copy under a new name. Flattened highlights cannot be undone later, and even annotation highlights are easy to lose track of in a long document.

To highlight any PDF for free, including scans, open the PDF Editor, choose Highlight Pen, drag across the text and save. Use Preview, Acrobat Reader or Edge instead when the reader should be able to delete your highlights later. To remove a highlight, click it and delete it; if it will not select, it is part of the page, and you need the original file. If a PDF will not let you highlight at all, it is either a scan or a restricted file, and Unlock PDF handles the second case.