Removing metadata from a PDF

What commands must I issue irreversibly to remove all metadata from foo.pdf? Assume embedded images are already clean. I got the impression from https://gist.github.com/hubgit/6078384 that exiftool -all:all= foo.pdf qpdf --linearize foo.pdf bar.pdf might suffice, but it wasn't clear to me whether it was an entirely complete method. There was some talk of pdftk and an "info dictionary" that I didn't understand.