New version of converters/wkhtmltopdf has been released upstream. see: https://github.com/wkhtmltopdf/wkhtmltopdf/releases/tag/0.12.3 It looks like the developer is not making release tarballs any longer -- not sure if this is intentional or simply an accidental omission. Might need to build from git using submodule (git clone --recursive)?
Updated, now 0.12.3.2