- Does my PDF get uploaded to a server?
- No — never. This tool runs entirely in your browser using pdf.js and pdf-lib, both of which execute locally. Your file bytes never leave your device over the network. This makes it safe to use with confidential documents, contracts, medical forms, and other sensitive PDFs.
- Will my handwriting annotations survive in other PDF readers?
- Yes. When you click "Save PDF", pdf-lib converts every stroke into a standard PDF content stream (vector drawing instructions). The result is a plain PDF that any reader — Adobe Acrobat, Preview on macOS, Chrome's built-in viewer, or a printer — can open and display. Strokes are flattened into the page, not stored as a separate annotation layer, so they cannot be accidentally hidden or removed.
- Does it work with Apple Pencil and pressure sensitivity?
- Yes on supported devices. The tool uses the Pointer Events API (
pointermove with pointerType === "pen") to capture stylus input. On iPads running Safari with an Apple Pencil, pressure (pressure) and tilt (tiltX/tiltY) values are read and used to modulate stroke width, giving a natural handwriting feel. On non-Pencil input (mouse or finger) the stroke width stays at the size you pick in the toolbar.
- What PDF page sizes and orientations are supported?
- All standard sizes (A4, Letter, Legal, A3, A5 and any custom size) and both portrait and landscape orientations work. Each page is rendered at 1.5× pixel density for sharp display and the annotation coordinates are mapped back to PDF points (1 point = 1/72 inch), so your strokes land in exactly the right position regardless of page dimensions.
- What tools are available?
- Pen — a precise anti-aliased ink stroke in any colour and width. Highlighter — a semi-transparent wide stroke for marking text, like a physical highlighter. Text box — click anywhere to type a note; press Enter or click outside to commit it as a text annotation. Eraser — removes the last stroke you drew on the current page (undo-style). The separate Undo button removes strokes one at a time; "Clear page" wipes all annotations from the current page.
- Can I annotate multiple pages?
- Yes. All pages of the PDF are rendered and stacked vertically. You can draw on any page independently. When you save, every page — with or without annotations — is included in the downloaded file, preserving the original page count and order.