pdf-signing

name	pdf-signing
description	Sign a local PDF contract or form by placing an existing handwritten signature image onto one or more pages, then visually verify the result. Use when Lorenzo asks to sign a PDF in Downloads, adjust signature placement, or reuse an existing local signature image for a fast non-cryptographic signature workflow.

PDF Signing

Use this when the task is to place an existing signature image onto a PDF. This is for visual signing only, not for cryptographic digital signatures.

Workflow

1. Find the target PDF, usually in ~/Downloads.
2. Use the default signature image at /home/lorenzo/Documents/General/signature_tight_crop_transparent.png.
3. If that file is missing, find another existing signature image. Prefer a transparent PNG.
4. Inspect the signature page before editing:
   • Render the relevant page with pdftoppm -png.
   • Use view_image on the rendered page.
5. Place the signature with scripts/place_signature.py.
6. Render the edited page and verify the placement visually.
7. Save to a new output PDF unless Lorenzo explicitly asks to overwrite the source.
8. If python3 does not have fitz/PyMuPDF, run the script through uv instead of trying to mutate the system Python.

Commands

Apply one or more signatures:

python3 /home/lorenzo/codex_skills/skills/pdf-signing/scripts/place_signature.py \
  --input "/path/to/input.pdf" \
  --output "/path/to/output.pdf" \
  --signature "/home/lorenzo/Documents/General/signature_tight_crop_transparent.png" \
  --page 3 \
  --rect 76,320,220,352 \
  --rect 76,478,220,510

If fitz is missing from python3, use:

uv run --with PyMuPDF python3 /home/lorenzo/codex_skills/skills/pdf-signing/scripts/place_signature.py \
  --input "/path/to/input.pdf" \
  --output "/path/to/output.pdf" \
  --signature "/home/lorenzo/Documents/General/signature_tight_crop_transparent.png" \
  --page 1 \
  --rect 686,146,818,175

Render a page for visual checking:

mkdir -p /tmp/pdf_signing_preview
pdftoppm -f 3 -l 3 -png "/path/to/output.pdf" /tmp/pdf_signing_preview/page

Then open /tmp/pdf_signing_preview/page-3.png with view_image.

Notes

• Default signature asset: /home/lorenzo/Documents/General/signature_tight_crop_transparent.png.
• --page is 1-based.
• Each --rect is x0,y0,x1,y1 in PDF points.
• PyMuPDF uses a top-left origin with y increasing downward.
• Verified ETH monthly timesheet supervisor signature rectangle on the current SAP landscape A4 form:
  • page 1
  • rect 686,146,818,175
• Prefer matching the size and baseline of any existing handwritten signature already present in the document.
• If the user asks for a true digital signature, stop and say this skill only handles visual signature placement.