- Is this tool really free with no watermark and no sign up?
- Yes, completely. There is no account, no paywall, and no watermark stamped on your output. The tool is built on two open-source libraries — PDF.js (Mozilla) and pdf-lib — that run entirely inside your browser tab. We never receive your file. Knackpad is supported by advertising, not by charging you or degrading your PDFs.
- Does my PDF get sent to a server?
- No. When you choose a file, your browser reads it directly from your local disk using the File API. The raw PDF bytes stay on your machine at all times. There is no backend processing, no cloud storage, and no analytics attached to the file content. This makes it safe for confidential, legal, medical, or financial documents.
- What drawing tools are available?
- Four tools: Pen — opaque freehand strokes in any color and thickness, ideal for signatures, arrows, circles, and handwritten notes. Highlighter — semi-transparent yellow (or any color) strokes for marking up text. Text — click anywhere to place a text box and type; multi-line supported. Eraser — scrub out any pen or highlight stroke you drew. Undo (Ctrl+Z or Cmd+Z) removes the last full stroke or text entry.
- Does it work on iPad with Apple Pencil?
- Yes. The drawing canvas uses the W3C Pointer Events API, which Safari on iPadOS supports natively. Apple Pencil input is treated as a pointer event, so drawing feels responsive and natural. To prevent the page from scrolling while you draw, the canvas uses
touch-action: none. Pressure sensitivity is not mapped to line width in the current version — use the Size slider to set your stroke thickness before drawing.
- How are the drawings saved into the PDF?
- When you click "Download PDF", pdf-lib reads the original PDF pages unchanged and overlays your annotations as native PDF drawing operators —
moveto/lineto paths for pen strokes and the built-in Helvetica font for text. This means the annotations are vector content: they remain crisp when you zoom in, print at any DPI, or open the file in any PDF viewer. The underlying PDF content is not re-encoded or re-compressed.
- Can I draw on every page of a multi-page PDF?
- Yes. Use the ← → arrows in the page navigation bar to move between pages. Each page maintains its own set of annotations independently. When you click "Download PDF", all annotated pages are combined into a single output file. Pages with no annotations are passed through unmodified.
- Can I edit or remove the existing text in my PDF?
- No. This tool adds new content on top of existing PDF pages — it does not reflow, edit, or delete the original PDF's text or images. If you need to change body text inside a PDF, you need a full PDF editor such as Adobe Acrobat. For signing, annotating, circling, highlighting, or adding freehand notes, this tool is the right choice.