pdf-sign

What

A tool to sign PDF files. We are here referring to the visible, non-cryptographic squiggles.

How

First, create one or several signatures in the form of small PDF files with transparent backgrounds. The recommended way is:

• Use the included pdf-create-empty tool to create an empty, transparent PDF file. If 3×2 inch suits you, you can use empty-3inx2in.pdf directly.
• Use an application of your choice to sign it. You can for example use Okular's Freehand Line, or transfer it to your smartphone and use Adobe Acrobat Reader.
• Put the signed file in ~/.pdf_signatures/.

You can now use the pdf-sign tool interactively (or non-interactively) to sign PDF files.

Run pdf-sign -h or pdf-create-empty -h for details.

Installation:

• Install dependencies: python3.7 or later with module tkinter, gs (Ghostscript), pdftk and pdfinfo.
• Copy one or both tools to a directory in your $PATH.

Installation on Debian:

apt-get update && apt-get install -y coreutils ghostscript git pdftk poppler-utils python3 python3-tk
git clone https://github.com/svenssonaxel/pdf-sign.git
cd pdf-sign
cp pdf-sign pdf-create-empty /usr/local/bin/

Why

There appears to be a lack of applications that run on Linux and allow for attaching free-hand signatures to PDF files in a good way.

(Non-)alternatives include:

• Okular: Allows for drawing 'Freehand Line' annotations, but not saving those for later use. Allows for inserting custom saved stamps, but these will not be visible in other PDF readers.
• Evince: Allows for certain kinds of annotations, but nothing that can serve as a signature.
• pdftk, ghostscript, and other command-line tools: Allows for inserting stamps, but not interactively selecting where.