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.
• 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: Copy one or both tools to a directory in your $PATH. Dependencies:

• python3
• pdftk
• gs (ghostscript)
• mv (coreutils)
• pdfinfo (poppler-utils)

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.