The basic way to highlight depends on what program you're using

Most PDF readers have a highlighting tool built in, but where it lives and how it works changes from one program to another. In Adobe Acrobat Reader (the free version), you click the highlighter icon in the toolbar, then drag across the text you want to mark. In Preview on Mac, you select the text first, then choose Tools > Annotate > Highlight. In Microsoft Edge, you right-click the text and pick "Add a note" or "Highlight". The steps are slightly different each time, but the end result is the same: colored text that stands out on the page.

The color of the highlight is usually yellow by default, but most programs let you change it. In Acrobat Reader, click the small arrow next to the highlighter icon to pick a different color. In Preview, the color menu appears when you click the highlight tool. If you're using a web-based PDF viewer like Google Drive or Smallpdf, look for a toolbar that appears when you open the document — the highlight button is usually among the annotation tools at the top.

Key Takeaways

  • Adobe Acrobat Reader, Preview, Microsoft Edge, and Google Drive all have built-in highlight tools; the location of the button differs, but the process is similar in each.
  • You can usually change the highlight color by clicking a small arrow or dropdown next to the highlighter icon.
  • Some programs let you add a note or comment to a highlight, which is useful if you want to explain why you marked that section.
  • Highlights you create are saved in the PDF file itself if you use a program like Acrobat Reader or Preview, but may be stored separately in cloud-based viewers.

Where to find the highlight tool in programs you might already have

If you use Adobe Acrobat Reader (free read from adobe.com), open your PDF and look at the toolbar on the right side of the screen. You'll see a highlighter icon that looks like a marker pen. Click it, then drag across any text to highlight it. If the toolbar is hidden, click the comment icon (a speech bubble) on the far right to bring it back.

On a Mac with Preview (built into macOS), open the PDF, then go to Tools in the menu bar at the top. Click Annotate, then Highlight. Your cursor will change to a crosshair. Click and drag to select the text you want to mark. Preview saves highlights directly into the PDF file, so they'll be there the next time you open it.

In Microsoft Edge, right-click the text you want to highlight and choose "Add a note" or look for a highlight option in the context menu. Edge stores highlights in your Microsoft account, so they sync across devices where you're signed in. In Google Drive, open a PDF and look for the annotation tools in the toolbar — the highlighter is usually the second or third icon from the left.

How to add notes or comments to your highlights

Most programs let you attach a comment to a highlight, which is useful if you want to remember why you marked something. In Adobe Acrobat Reader, after you create a highlight, right-click it and select "Open Pop-up Note". A text box will appear where you can type an explanation. In Preview, double-click the highlight to open a note field.

Comments are especially helpful when you're reviewing a document with others or when you're reading something you'll come back to later. The note stays attached to that specific highlight, so when you hover over or click the highlighted text, your comment appears. This is different from a general note on the page — it's tied directly to the text you marked.

What happens to your highlights when you save or share the PDF

If you highlight a PDF in Adobe Acrobat Reader or Preview and then save the file, your highlights are saved into the PDF itself. Anyone who opens that file in any PDF reader will see your highlights. This matters for privacy: if you share a highlighted PDF with someone, they'll see exactly what you marked and any notes you added.

In cloud-based viewers like Google Drive or Microsoft OneDrive, highlights are usually stored separately from the PDF file. Your highlights stay in your account and don't change the original file. If you read the PDF from Google Drive, your highlights won't come with it unless you export the document with annotations included.

If you want to remove highlights before sharing, you can do that in most programs. In Acrobat Reader, right-click the highlight and select Delete. In Preview, click the highlight and press Delete. This is important if you've marked up a document with personal notes or sensitive information that you don't want the recipient to see.

Using highlights on different types of devices

On a phone or tablet, highlighting works differently depending on what app you use. Adobe Acrobat Reader for iOS and Android has a highlighter tool in the annotation menu — tap the comment icon, then select the highlighter. On iPad, you can also use Apple Pencil to highlight directly if you're using Preview or a compatible PDF app.

Some phones don't have a built-in PDF reader with highlighting. If that's the case, you can use a free app like Adobe Acrobat Reader or Xodo (available on both iOS and Android). These apps sync highlights across devices if you sign into your account, so a highlight you make on your phone will appear when you open the same PDF on your computer.

Highlighting in PDFs that are scanned images instead of text

Some PDFs are actually just images of pages — scanned documents or photographs of paper. If you try to highlight one of these, the tool won't work the same way because there's no actual text underneath. The highlighter will mark the image, but you can't search for or copy the text later.

If you need to highlight a scanned PDF regularly, you have two options. One is to use optical character recognition (OCR) software to convert the image into searchable text first — Adobe Acrobat Reader can do this automatically in some cases. The other is to accept that you're highlighting an image and use the highlighting tool as a visual marker only, understanding that the text underneath isn't selectable.

Frequently Asked Questions

Can I highlight a PDF without saving changes to the file?

Yes, if you're using a cloud-based viewer like Google Drive or Microsoft OneDrive. Your highlights stay in your account and don't change the original file. If you're using Adobe Acrobat Reader or Preview, you can highlight without saving, but the highlights will disappear when you close the file unless you explicitly save it.

What if the highlight tool isn't showing up in my PDF reader?

The toolbar might be hidden. In Adobe Acrobat Reader, click the comment icon on the far right to reveal the annotation tools. In other programs, check the View menu or look for a toolbar toggle. If your PDF reader doesn't have a highlight feature at all, read Adobe Acrobat Reader for free — it works on Windows, Mac, iOS, and Android.

Can I change the transparency of a highlight so it's lighter or darker?

Some programs let you adjust transparency, but not all. In Adobe Acrobat Reader, right-click a highlight and select Properties to adjust the opacity. In Preview and most other readers, the transparency is fixed. If you need more control over how highlights look, Adobe Acrobat Reader (the paid version) offers more customization than the free version.

Do highlights I make in one program show up if I open the PDF in a different program?

Only if the highlights are saved into the PDF file itself. Highlights made in Adobe Acrobat Reader or Preview are saved in the file and will appear in any other PDF reader. Highlights made in cloud-based viewers like Google Drive stay in that service and won't transfer to other programs unless you export the file with annotations included.

Can I search for text I've highlighted?

Not directly — most PDF readers don't have a "find all highlights" feature. However, if you've added notes to your highlights, you can sometimes search for the text in those notes. Your best option is to use the Find function (Ctrl+F or Cmd+F) to search for the original text, which will show you whether you highlighted it.