PDF is also plain text file, with one slight caveat that PDF page index contains byte offsets into the file.
[Edit: this observation should probably be taken as relative to various other "plain-text with byte offsets as decimal ASCII number" I have seen, with PDF being the most sane from the set of such formats I've seen, with Netscape/Mozilla Mork beeing the most insane]
[Edit: this observation should probably be taken as relative to various other "plain-text with byte offsets as decimal ASCII number" I have seen, with PDF being the most sane from the set of such formats I've seen, with Netscape/Mozilla Mork beeing the most insane]