Flint PDF

Annotate PDF

Add boxes, arrows, highlights, and freehand notes.

Flint's PDF annotator lets you mark up any document straight from your browser. Drop in boxes, arrows, highlights, or freehand strokes, swap colors and stroke widths on the fly, and keep the original untouched. It's the fastest way to leave clear feedback on a contract, a syllabus, or a design proof without installing anything.

  • Box, highlight, line, arrow, and freehand drawing
  • Seven preset colors plus an adjustable stroke width
  • Click any annotation to remove it
  • Original kept as a previous version
  • Browser-based — no install
  • Files private to your account
  • Up to 250 MB on Pro
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Drop your PDF, or click to choose
Files stay private to you. You can come back to them any time.

How it works

Right in your browser, no install

Flint PDF runs entirely in your browser. Drop a file in, do the thing, get the file out.

  1. 1

    Upload your PDF

    Drag a file into Flint or pick one from your device. Pages render in seconds and stay on your side of the connection while you work.

  2. 2

    Mark it up

    Pick a tool — box, highlight, arrow, line, or freehand — choose a color and stroke width, then draw directly on the page. Click any annotation to remove it.

  3. 3

    Apply your changes

    Hit Apply and Flint bakes the annotations into a new version. Your original is preserved as a previous version you can roll back to anytime.

  4. 4

    Download the result

    Export the annotated PDF with a Pro plan. Share, print, or send it on — the markup travels with the file in any viewer.

What it's for

Built for real work

Review contracts and agreements

Circle the clauses you want changed and drop arrows where a counter-signature is missing. Send the marked-up copy back without retyping a thing.

Mark up design and creative work

Highlight problem areas in a mockup, sketch a quick fix freehand, and box the regions a designer needs to revisit. Faster than a screenshot tool plus paint.

Study notes and lecture handouts

Highlight key passages, underline definitions, and scribble margin notes on lecture PDFs. Keep the original clean for later review.

FAQ

Frequently asked questions

Is the PDF annotator free?
Annotating is free. Exporting the final annotated PDF requires a Pro plan, so you can try the full experience before deciding to upgrade.
Are my files private?
Yes. Files are processed for your session only and aren't shared with third parties. Originals stay accessible to you as previous versions.
Do I need to install anything?
No. Flint runs in any modern browser on Mac, Windows, Linux, and ChromeOS. There's no plugin, no desktop app, and no extension required.
What's the maximum file size?
Pro accounts can upload PDFs up to 250MB. That covers most contracts, scanned documents, and multi-hundred-page reports.
Can I annotate scanned PDFs?
Yes. Annotations are drawn on top of the page, so they work the same whether the PDF contains real text or a scanned image.
Will the annotations be visible in other PDF viewers?
Yes. When you apply changes, Flint bakes the annotations into the PDF itself. They render the same in Acrobat, Preview, Chrome, and any standard viewer.
Can I undo an annotation?
Click any annotation to remove it before applying. After applying, you can roll back to the previous version of the document from your version history.

More from Flint PDF

More PDF tools

Built browser-side, share the same editor.

Edit

Change what's on the page.

Organize

Rearrange or combine pages and files.

Export

Optimize or convert for sharing.

Annotate PDF Online — Free PDF Annotator | Flint — Flint PDF