How it works
The PDF Annotator lets you draw freehand annotations directly onto PDF pages using a digital pen tool โ with configurable ink color and line width โ and saves the drawings back into the PDF as raster image overlays. Use it to circle important passages, cross out incorrect values, sketch correction marks, add arrows pointing to specific areas, or sign a document with a hand-drawn signature across multiple pages.
How it works: each page renders to a background canvas using PDF.js. A transparent drawing canvas overlays it. You draw on the drawing canvas; your strokes are stored per-page. When navigating between pages, the current page's drawing is saved as a data URL and restored when you return. When you click Download Annotated PDF, each annotated page has its drawing canvas converted to a PNG image and embedded into the page using pdf-lib, at the exact page coordinates.
Drawing controls: - Color: any CSS color โ use red for corrections, blue for additions, yellow for highlights (at reduced opacity) - Line width: 1โ12 pixels. Narrow for precise annotations; wide for obvious markup or highlighting
Multi-page annotation: navigate between pages with the arrow controls. Your annotations on earlier pages persist in memory. All annotations across all pages are embedded when you download.
Limitations: annotations are embedded as raster PNG overlays, not as PDF annotation objects. This means they are not editable after download and will not appear in PDF readers' annotation panels. For annotation objects (sticky notes, text boxes), a desktop PDF editor is required.
Privacy: page rendering uses PDF.js; annotation embedding uses pdf-lib. All processing occurs in the browser. No page content is uploaded.
Frequently Asked Questions
- No. Annotations are embedded as raster PNG image overlays, not as PDF annotation objects (the type that appear in Acrobat's comment panel and are editable). The drawing canvas is converted to a PNG and embedded as an image stamp over the page. This means annotations are permanently baked in, are not listed in the annotations panel, and cannot be selected or edited after download. For proper annotation objects, use a desktop PDF editor.
- Yes. The PNG overlay is embedded in the PDF page content at the page coordinate level, not as a screen-only layer. It prints on all printers at the configured opacity (100% by default since the drawing canvas is fully opaque where ink was applied). Your freehand drawings will appear in print exactly as they appear on screen.
- Yes. When you navigate away from a page, your drawing is saved as a data URL in memory and restored when you return. All pages' annotations persist until you download or reload the page. Navigate freely between pages โ each page maintains its own drawing layer.
- This tool supports only freehand drawing โ click and drag to draw continuous strokes. For straight lines or geometric shapes (rectangles, circles, arrows), a desktop PDF editor with a shape annotation tool is required. For simple correction marks and rough circles, freehand drawing is sufficient.