PDF Sign

Sign and fill PDF forms programmatically. Works on both digital PDFs (with a text layer) and scanned PDFs (via OCR).

Signature image

Always ask the user where their signature image is — never assume a location, and never commit a signature image to a repository. A scanned signature (dark ink on white) works best.

If the image has a white background (typical JPG scan), convert it to a transparent PNG first — otherwise the overlay blanks out any text or lines beneath it:

from PIL import Image
img = Image.open(SRC_JPG).convert("RGBA")
img.putdata([(0, 0, 0, 0 if (r+g+b)//3 > 200 else 255-(r+g+b)//3)
             for r, g, b, a in img.getdata()])
img.save(OUT_PNG)

Save the transparent version next to the original so it can be reused.