You search for "highlighter for PDF files" and find dozens of tools claiming to support highlighting. But when you actually try them, you discover three common problems:
This guide tests 6 popular free PDF highlighter tools against these three criteria, plus offline capability and file size limits.
| Feature | PDF Agile | Adobe Acrobat Reader | Foxit Reader | Xodo | Mac Preview | Edge Browser |
|---|---|---|---|---|---|---|
| Multi-color highlighting | ✓ 5 colors | ✓ Yes | ✓ Limited | ✓ Yes | ✓ 5 colors | ✗ 1 color |
| Highlight scanned PDFs | ✓ Auto-OCR | ✗ No | ✗ No | ✗ No | ✗ No | ✗ No |
| Export highlights to TXT/CSV | ✓ Yes | ✗ Paid only | ✗ No | ✓ PDF only | ✗ No | ✗ No |
| Works offline | ✓ Yes | ✓ Yes | ✓ Yes | ✓ App only | ✓ Yes | ✓ Yes |
| Sticky notes with author | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Basic | ✗ No |
| Free tier | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Built-in | ✓ Built-in |
| File size limit | ✓ No limit | ✓ No limit | ✓ No limit | ✓ 100MB | ✓ No limit | ✓ No limit |
Download and install PDF Agile from the official site. Free, no sign-up required.
Open your PDF. If it's a scanned image, OCR runs automatically — you'll see text become selectable within seconds.
Select text and highlight. Drag across the text you want to mark, then click the Highlight icon and pick your color (yellow, green, blue, pink, red).
Export highlights. Click File → Export Comments to save all highlights and their page numbers as a TXT or CSV file for your study notes.
Open your PDF in Adobe Acrobat Reader (free version).
Select text → right-click → "Highlight Text". Choose color from the Comment toolbar.
To export: you need Acrobat Pro (paid) — the free version cannot export highlights separately.
Limitation: Adobe Reader cannot highlight scanned PDFs. If your PDF is an image, you need OCR first — PDF Agile handles this automatically.
Double-click any PDF on Mac — Preview opens automatically.
Click the Markup toolbar button (pen icon) → select the Highlight tool → pick a color.
Drag across text to highlight. Preview supports 5 colors but cannot export highlights separately.
Limitation: Preview works well for basic highlighting on text PDFs, but lacks export and scanned PDF support. For those features, use PDF Agile on Mac.
Scanned PDFs are images — you can't select text in them. Most highlighter tools simply don't work on scanned files. Here's how to handle this:
Yes. Xodo (Android/iOS) and PDF Agile (Windows) both support mobile highlighting. On iPhone, you can also use the built-in Files app to add basic highlights.
Most likely your PDF is a scanned image, not text-based. You need OCR to convert the image into selectable text first. PDF Agile runs OCR automatically — other tools require a separate OCR step.
PDF Agile can export all highlights with page numbers to TXT or CSV. Adobe Acrobat Pro can export to a summary PDF (paid feature). Most other free tools cannot export highlights separately.
Yes — PDF Agile, Adobe Acrobat Reader, and Foxit Reader all offer free highlighting on Windows 10. PDF Agile is the only one that also handles scanned PDFs and exports highlights.
Bottom line: If you need to highlight scanned PDFs or export your highlights, PDF Agile is the only free tool that handles both. For basic text-based highlighting, Adobe Reader and Mac Preview work fine.
Free · No subscription · Handles scanned PDFs · Export highlights