The document information dictionary in a PDF file specifies various pieces of information about a PDF. These can be consulted in a PDF viewer (for instance, Acrobat).
Here is a summary of the commands for setting entries in the document information dictionary:
(The details of the format for creation and modification dates can be found in Appendix A. Using the date "now" uses the time and date at which the command is executed.)
For example, to set the title, the full command line would be
cpdf -set-title "A Night in London" in.pdf -o out.pdf
The text string is considered to be in UTF8 format, unless the -raw option is added—in which case, it is unprocessed.