Highlight PDF

Free

Drag to add yellow / green / pink / blue highlights on page 1. Multiple highlights per session, opacity adjustable, lossless overlay.

What you'll get: a PDF with yellow / green / pink / blue highlight rectangles drawn over page 1 — drag to add multiple highlights, adjustable opacity, lossless overlay. For another use, try Add Text to PDF.

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Stays in your browser

Free tools run fully on-device — nothing is uploaded to a server.

No watermarks

Clean output, no branding, no daily limits.

Free forever

No signup required. Seriously.

Why people highlight PDFs

Highlighting calls attention to specific passages without modifying the underlying text. Translucent overlays let the original content show through — perfect for emphasizing key sentences in a contract, marking action items in meeting notes, or flagging passages during research.

Reading + study

Mark key passages while reading research papers, textbooks, and reference docs. Save the highlighted version for later review.

Contract review

Highlight clauses that need negotiation or follow-up before sending the redlined version back to counterparty.

Meeting notes

Highlight action items and decisions in shared meeting minutes so reviewers spot them at a glance.

Invoice / statement review

Mark line items in question on a vendor invoice or bank statement before raising a dispute.

Editorial markup

Highlight passages that need editing in a draft. Different colors = different concerns (factual vs. style vs. tone).

Reference flagging

Highlight specific quotes or stats in a long source document to find them quickly later.

How Highlight PDF works

Three steps, no signup, no uploads.

STEP 1
Drop your PDF
Up to 100 MB. PDFium renders page 1 at 1.5× as the editor canvas.
STEP 2
Drag to add highlights
Click and drag anywhere on the page to draw a translucent rectangle. Drag again to add more — multiple highlights supported. Use Clear All to start over.
STEP 3
Pick color + opacity
Yellow (default), green, pink, or blue. Opacity 10–80% — lower = more readable underlying content.
STEP 4
Apply & download
We draw translucent rectangles on page 1 via pdf-lib drawRectangle. Lossless overlay — original content untouched.

What makes pdfcraft ai different

Same engine Chrome uses
PDFium is Google's PDF engine — the one that powers Chrome's built-in PDF viewer. We compile it to WebAssembly so it runs in your browser at near-native speed.
100% local processing
Most free PDF tools upload your file to a server, process it, and stream the result back. We don't. Your file lives in your browser tab and never touches our infrastructure. Verifiable in your browser's Network panel.
No watermark, no signup, no daily limit
Convert 1 PDF or 1,000. We don't gate on volume because there's nothing to gate on — the engine runs on your machine.
Honest about limitations
When something the tool can't do (encrypted PDFs, cross-reference streams), we tell you clearly instead of failing silently. Same for partial results: sampled vs exact, embedded vs not.
Open standards, free engines
PDFium is BSD/Apache licensed (free for any use). We don't pay vendor license fees and pass that savings on to you (and to ourselves) as a free, ad-supported tool with no upgrade-to-pro pressure.

Frequently asked questions

Does this highlight every page or just page 1?

v1 = page 1 only. Multi-page highlighting needs page navigation in the editor (e.g. prev/next buttons), which is a v2 enhancement once we have multiple visual editors validating the navigation pattern. For now, if you need to highlight page 5, run our Extract Pages tool first to isolate page 5, highlight it, then merge it back.

Is this real text-aware highlighting or just rectangles?

Just rectangles. True text-aware highlighting (where you click+drag along a sentence and the highlight follows the text bounds) requires PDFium text-position math we haven’t shipped yet. Drag-rectangle covers most users’ needs — they want to draw over a region they care about, not select specific words.

Can I delete an individual highlight without clearing all?

Not in v1 — there’s a Clear All button only. Per-highlight deletion (click on a highlight to remove it) is a v2 enhancement.

Will the highlights survive in viewers other than yours?

Yes. We draw using pdf-lib’s standard rectangle primitive with opacity. Acrobat, Apple Preview, Chrome, Firefox, and every printer we’ve tested respect it correctly.

Is the highlight an annotation or a page-content overlay?

Page-content overlay (drawn into the content stream). It’s permanent and not editable as an annotation in viewers like Acrobat. If you need editable annotations, that’s a different tool (PDF.js-backed annotation editor — future work).

Is anything uploaded?

No. PDFium renders the preview locally; pdf-lib applies the rectangles locally.

Need to redact instead?

Redact PDF (coming soon) covers the ‘black box over sensitive info’ case. Highlight is for emphasis; Redact is for hiding.

Try Add Text to PDF

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