PDF Lab: Free Browser-Based PDF Editor, Annotator and Signer

PDF Lab is a free, browser-based PDF editor that lets you annotate, sign, highlight, draw on, and insert content into any PDF — without uploading the file to a server. Everything runs locally in your browser using Fabric.js and pdf-lib, so your document never leaves your device.

What can you do with PDF Lab?

PDF Lab includes nine annotation and editing tools:

• Text — add styled text boxes anywhere on the page; choose font size and colour
• Draw — freehand drawing with a configurable brush size and colour
• Signature — draw a signature with your mouse, type your name in a handwriting font, or upload a saved signature image; initials are supported separately
• Highlight — five markup types: text highlight (yellow), underline, strikethrough, squiggly, and block highlight
• Eraser — block eraser for large areas and a freehand eraser for precision
• Shape — insert rectangles, circles and custom shapes as overlays
• Image — upload an image and position it anywhere on the page
• Hyperlink — draw a link region and attach a URL to it

How to annotate a PDF

1. Go to multi-toolkit.com/pdf-lab and click Open PDF to load your file.
2. Navigate pages using the thumbnail sidebar on the left.
3. Select a tool from the toolbar at the top or right side.
4. Draw, type or place your annotation directly on the canvas.
5. Repeat for other pages as needed, then click Export PDF to download the annotated file.

How to sign a PDF

Click the Signature tool in the toolbar. A panel opens with three tabs:

• Draw — use your mouse or trackpad to draw your signature in the canvas
• Type — type your name and it appears in a handwriting font
• Upload — upload a PNG or SVG of your existing signature

Once saved, your signature appears in the saved-signatures list so you can reuse it on other pages without redrawing. The same panel handles initials separately if you need to initial multiple pages.

Is PDF Lab private?

Yes. PDF Lab is 100% client-side. The file you open stays on your device at all times. No upload happens, no server receives your PDF, and no data is stored anywhere. The exported PDF is generated entirely in your browser by pdf-lib and downloaded directly to your computer.

This makes PDF Lab suitable for sensitive documents — contracts, medical forms, legal filings — where you would not normally send a file to a third-party service.

Supported PDF types

PDF Lab can open any standard PDF. For multi-page PDFs, thumbnails appear in the left sidebar and each page can be annotated independently. All annotations across all pages are merged into the final exported file. Very large PDFs (100+ pages) may be slower to render since Fabric.js renders the page as a canvas element — performance depends on your device.