cairo:pdf-surface-set-metadata (surface metadata utf8)

surface -- a cairo:surface-t instance
metadata -- a cairo:pdf-metadata-t value with the metadata item to set
utf8 -- a string for the metadata

Set document metadata. The :create-date and :mod-date values must be in ISO-8601 format: YYYY-MM-DDThh:mm:ss. An optional timezone of the form "[+/-]hh:mm}" or "Z" for UTC time can be appended. All other metadata values can be any UTF-8 string.

(cairo:pdf-surface-set-metadata surface :title "My Document")
(cairo:pdf-surface-set-metadata surface :create-datea "2015-12-31T23:59+02:00")