Add a new attachment (embedded file) to an existing PDF file. See also:
pdfdetach,pdfimages,pdfinfo. More information: https://manned.org/pdfattach.
pdfattach {{path/to/input.pdf}} {{path/to/file_to_attach}} {{path/to/output.pdf}}
pdfattach -replace {{path/to/input.pdf}} {{path/to/file_to_attach}} {{path/to/output.pdf}}
pdfattach {{[-h|--help]}}
pdfattach -v