How to Highlight Text in a PDF (Free, Every Device)

Highlighting a PDF sounds like it should need expensive software. It doesn't — the highlighter is one of the few markup features that's free in practically every PDF viewer ever made. The only real question is whether your PDF has selectable text. Let's start there, because it decides everything.

Step 0 — Can you select the text?

Try to click-drag across a sentence. If the words turn blue, you have a text-based PDF and every method below works instantly. If nothing selects, it's a scanned image and you have two choices: run OCR to add a real text layer first, or use a freehand highlight box (covered later).

Highlight on a Mac — Preview (already installed)

Preview ships with every Mac and highlights text in two clicks.

Highlight on Windows — free Adobe Acrobat Reader

Acrobat Reader is free (Acrobat Pro is the paid one). Reader's highlighter has no restrictions.

1. Open the PDF in Adobe Acrobat Reader.
2. In the toolbar, click the Highlight tool (a marker icon). On newer Reader it's under the highlighter/marker button in the top bar.
3. Drag across the text you want to mark.
4. To change color, right-click a highlight → Properties → pick a color, and optionally set it as the default.
5. File → Save.

Reader also lets you add a note to any highlight — right-click → Add Note — handy for review comments.

Highlight in the browser

Browser PDF viewers have caught up. Behavior varies by browser:

• Microsoft Edge has the strongest built-in support: select text → a small toolbar pops up with a Highlight button and color choices. Save with the download icon to keep them.
• Chrome and Firefox can view and (in recent versions) annotate PDFs, but highlight support is more limited than Edge or a dedicated reader. If your browser won't highlight, fall back to Preview or Reader.

Highlight on your phone

• iPhone / iPad: open the PDF in Files, Books, or Mail → tap the Markup pen → tap the highlighter → swipe across text. Share or save when done.
• Android: the free Adobe Acrobat Reader app has the same Highlight tool as desktop. Tap the marker, drag across the words, save.

Exporting and sharing with highlights kept

Highlights are saved inside the PDF as annotations, so anyone who opens the file sees them — no special export needed. Two things to watch:

• Save/Export, don't Print. "Print to PDF" usually flattens the page and can drop or alter annotations. Use the app's normal Save/Export.
• Sending for review? Highlights stay editable — the recipient can remove them. That's normally what you want for collaboration. If you instead need something permanently on the page, that's a different job (see below).

Highlighting vs redacting — opposite jobs

A highlight draws attention to text and leaves it fully readable and selectable underneath. That's great for study notes and review, but it is the wrong tool if your goal is to hide sensitive text — a colored highlight can be removed in seconds, and drawing a black box over text still leaves the words selectable and copyable beneath it.

When you need text truly gone, use Redact PDF. Real redaction removes the underlying content, not just covers it, so the words can't be selected, copied, or recovered. Use highlight to emphasize; use redact to erase.

Frequently asked questions

Do I need Adobe Acrobat Pro to highlight a PDF?

No. Highlighting is free in macOS Preview, the free Acrobat Reader, Microsoft Edge, and phone apps. Acrobat Pro adds nothing for basic highlighting.

Does pdfty have a highlighter tool?

No — we don't, and we won't pretend otherwise. Highlight your PDF free in Preview, Reader, or Edge. pdfty helps with the neighboring tasks: OCR to make a scan highlightable, Sign PDF to sign it, and Redact PDF to permanently remove text.

I can't select the text to highlight it — why?

Your PDF is a scanned image with no text layer, so there's nothing to select. Run it through OCR first to add a real, selectable text layer, then highlight normally. As a quick alternative, most markup tools also offer a freehand rectangle you can draw over the area.

Will my highlights show up when someone else opens the file?

Yes. Highlights are saved as annotations inside the PDF, so any standard viewer displays them. Just be sure you used Save/Export rather than Print to PDF, which can flatten or drop them.

Can the recipient remove my highlights?

Yes — highlights stay editable, which is usually what you want for review. If you need something that can't be changed, highlighting is the wrong tool; you'd want to flatten the document or, for hiding text, redact it.

How do I highlight a PDF on my phone?

On iPhone use the Markup highlighter in Files, Books, or Mail. On Android use the free Adobe Acrobat Reader app's Highlight tool. Both save a normal PDF with the highlights kept.

How do I permanently hide text instead of highlighting it?

Use Redact PDF. Unlike a highlight or a black box, real redaction deletes the underlying text so it can't be selected, copied, or recovered.