The basic way to highlight a PDF depends on what tool you're using
Most PDF readers have a built-in highlighter tool that works like a marker pen — you select text or draw over an area, choose a color, and the highlight stays with the document. The steps differ slightly between Adobe Acrobat Reader, Preview on Mac, and free tools like Foxit or Sumatra PDF, but the principle is the same. You open the document, find the highlighting tool in the toolbar or menu, and click or drag across what you want to mark.
Some tools let you highlight after selecting text; others require you to set up the highlighter first and then select. A few let you do both. The color options usually include yellow, green, pink, and blue, and some tools let you add a note or comment alongside the highlight so you remember why you marked it.
Key Takeaways
- Adobe Acrobat Reader's highlight tool is in the toolbar at the top; select text first, then click the highlighter icon and choose your color.
- Mac's Preview app has a highlight tool in the toolbar that works the same way — select text, then click the marker icon.
- Free tools like Foxit Reader and Sumatra PDF include highlighting but may require you to set up the tool before selecting text.
- Highlights save with the PDF file itself, so they stay visible when you open the document again or share it with someone else.
- Some tools let you search or filter by highlight color, which helps you organize notes by importance or category.
How to highlight in Adobe Acrobat Reader
Open your PDF in Adobe Acrobat Reader and look at the toolbar along the top. You should see a highlighter icon that looks like a marker pen — it's usually near the comment tools. Click on it, and a small menu appears with color options: yellow, green, pink, and blue. Select your color.
Now click and drag across the text you want to highlight. The highlight appears when ready. If you want to change the color of an existing highlight, right-click on it and select a new color from the menu. To remove a highlight, right-click it and choose Delete.
You can also highlight by selecting text first. Triple-click to select a full paragraph, or click and drag to select a few words. Once the text is highlighted in blue, click the highlighter tool and choose your color — the selection turns into a permanent highlight.
How to highlight in Preview on Mac
Open your PDF in Preview (the default Mac PDF reader) and look at the toolbar. You'll see a highlighter icon that looks like a marker. Click it to set up the highlighting tool. The cursor changes to show you're in highlight mode.
Click and drag across the text you want to mark. The highlight appears in yellow by default. To change the color, click the highlighter icon again and look for a color menu — you can usually access it through the Tools menu at the top of the screen. Select a different color, then highlight more text.
To remove a highlight in Preview, click the highlighter tool, then click and drag over the highlighted text again. This toggles the highlight off. If you want to add a note next to your highlight, use the text box tool (also in the toolbar) to add a comment.
How to highlight in free PDF tools
Foxit Reader and Sumatra PDF both include highlighting, but the process varies slightly from Adobe and Preview. In Foxit, open the document and look for the Comment menu or toolbar. Click the highlighter tool, choose your color, then click and drag across text. The highlight appears when ready.
Sumatra PDF works similarly — find the highlight tool in the toolbar (it may be under an annotation menu), set up it, and drag across text. Some free tools require you to save the file in a special format to preserve highlights, so check the File menu after highlighting to see if you need to export or save as a different type.
If your free tool doesn't have a visible highlighter, check the Tools or Annotations menu. Some tools hide the highlighting feature there instead of putting it in the main toolbar. If highlighting isn't available at all, you may need to switch to a tool that supports it — Foxit and Sumatra both do, and both are free.
Highlighting images and diagrams in PDFs
Most PDF tools can highlight text but not images the same way. If you need to mark up a diagram, photo, or chart, you have two options: draw a box around it or add a comment next to it.
To draw a box, look for a rectangle or shape tool in the toolbar (often near the highlighter). Click it, choose a color, and drag a rectangle around the image. This creates a visible border that marks the area without covering the image itself. Some tools let you use a freehand drawing tool instead, which lets you circle or underline parts of an image.
If you want to add context, use the comment or text box tool to write a note next to the image. This is often clearer than trying to highlight an image, because it explains why you marked it.
How to save and share highlighted PDFs
When you highlight text in a PDF using Adobe Acrobat Reader, Foxit, or Preview, the highlights are saved directly into the file. Close the document and reopen it — the highlights stay there. If you save the file with a new name, the highlights come with it.
When you share a highlighted PDF with someone else, they see your highlights when they open it. This works as long as they're using a tool that supports PDF comments and highlights — all major readers do. If someone opens your file in a very basic viewer that doesn't support annotations, the highlights may not show up, but they're still in the file.
If you want to remove all highlights before sharing, most tools have a way to do this. In Adobe Acrobat Reader, go to Tools, then look for an option to remove all markup or comments. In Preview, you can select and delete highlights one at a time, or export the PDF without annotations.
Organizing highlights by color and searching them
Using different colors for different purposes helps you organize your notes. For example, you might use yellow for definitions, green for important dates, and pink for questions you need to follow up on. This takes a few extra seconds per highlight but saves time when you're reviewing the document later.
Some PDF tools let you search or filter by highlight color. In Adobe Acrobat Reader, open the Comments panel (usually on the right side of the screen) and look for a filter option. You can then view only highlights of a specific color, which helps you find all the definitions or all the questions in a long document without scrolling through everything.
If your tool doesn't have a built-in filter, you can still use the Find function (Ctrl+F or Cmd+F) to search for keywords you highlighted. This is slower than filtering by color, but it works in any PDF reader.
Frequently Asked Questions
Can I highlight a PDF on my phone or tablet?
Yes. Adobe Acrobat Reader, Foxit, and most other PDF apps for iOS and Android include highlighting. The process is the same — tap the highlighter tool, choose a color, and tap or drag across text. Highlights save to the file and sync across devices if you use Adobe's cloud storage.
What if I highlight text and it doesn't save?
Some PDF readers don't save highlights by default. Check the File menu and look for an option to save, export, or flatten the document. If you're using a web-based PDF viewer, try downloading the file to your computer first, then highlighting it in a desktop app like Adobe Reader or Foxit, which always save changes.
Can I highlight a PDF that's locked or password-protected?
It depends on the permissions set by whoever locked it. Some locked PDFs allow highlighting but not printing or copying. If you can't highlight, the document owner restricted that feature. You can ask them for an unlocked version, or try copying the text into a word processor and highlighting it there instead.
Do highlights print when I print a PDF?
Yes, highlights print by default in most PDF readers. If you don't want them to print, check the Print dialog for an option to exclude comments or markup before you send the document to the printer.
Can I change the transparency of a highlight so I can see text underneath better?
Adobe Acrobat Reader lets you adjust highlight transparency through the comment properties. Right-click a highlight, select Properties, and look for an Opacity slider. Free tools like Foxit may not have this option, so you may need to use Adobe Reader if transparency control is important to your work.