First, recall user _apt was added recently. Second, not all comments
appear to have the same original; some ones refer access rights, so some
comments suggest change owner or ACL of some directory. However, another
comments point out something that appears to be a parsing error over the
directory
Just for the record. The «PDF Chain» message for an «input.pdf»
PDFTK returned error!
Input/Output Error
Error code: 256
may be removed by decrypting «input.pdf» with the command
qpdf --decrypt input.pdf output.pdf
as Manoj did for another, related problem
