PDF Highlighter & Annotator
Highlight text passages, mark tables, and add freehand marker annotations on PDF documents directly in your browser. Choose from neon yellow, mint green, sky blue, coral pink, and warm orange highlighter shades with complete document privacy.
How to use
Upload a PDF document by dragging it into the dropzone or clicking to select.
Choose your annotation tool: Box Highlight (for clean rectangular blocks) or Freehand Pen (for marker strokes).
Select your preferred highlighter color from the palette dots.
Click and drag across text, figures, or tables to highlight.
Navigate pages, undo any marks, and click 'Download Annotated PDF' to export.
Interactive client-side PDF highlighting
Reviewing contracts, research publications, invoices, and lecture slides often requires marking key clauses, definitions, and numbers. Rather than installing heavy desktop software or relying on third-party cloud services that store copies of your documents, this tool lets you annotate and highlight PDFs directly in your browser using local canvas and pdf-lib rendering engines.
Dual highlighting modes
Select the optimal tool for your document:
- Box Highlight: Drag rectangular boundary boxes across single or multi-line text blocks and financial tables for neat, aligned highlights.
- Freehand Marker Pen: Draw natural callout circles, arrows, underlines, and freehand notes with customizable line thickness (Thin 8px, Medium 14px, Thick 22px).
5 Curated highlighter shades
Organize your annotations with an accessible color-coded system:
- Neon Yellow (#facc15): Ideal for critical clauses, summary takeaways, and key dates.
- Mint Green (#4ade80): Recommended for approved items, positive metrics, and checkmarks.
- Sky Blue (#60a5fa): Great for technical definitions, references, and citations.
- Coral Pink (#f472b6): Highlights warnings, liabilities, and disputed clauses.
- Warm Orange (#fb923c): Marks action items and follow-up tasks.
Zero data transmission guarantee
All page conversions and transparent overlay merges execute locally within your device memory. No PDF documents or annotation data are transmitted over the network.
Frequently asked questions
Will the text underneath my highlights remain readable?
Yes. Highlights are rendered with calibrated semi-transparency (alpha 0.42), ensuring all text, numbers, and graphics beneath the highlight remain fully legible.
Can I undo or delete a highlight?
Yes. Click the 'Undo' button in the toolbar to step back through your highlights on the current page.
Can I annotate multi-page PDF documents?
Yes. Use the page navigation buttons (Page X of Y) to move between pages. Your highlights across all pages will be saved into the exported PDF.
Are my files stored on your servers?
No. All PDF operations run 100% locally in your web browser. No files are uploaded to any server.
Does this tool work on scanned PDFs or image-based documents?
Yes. Both Box Highlight and Freehand Marker work flawlessly across all PDF types, including vector text PDFs, scanned receipts, and image-based documents.