pdfx + hyperref prevents setting PDF metadata [incompatible packages]

Question

Edit: Apparently hyperxmp and pdfx are incompatible.

I'm using the pdfx, and then \hypersetup and the hyperxmp package to set metadata as I like. I've run into two issues.

1. The metadata doesn't seem to be set now I'm using pdfx.
2. 'pdftitle has already been set' etc. warnings.

Any suggestions?

MWE

\documentclass{scrartcl}
\usepackage[a-3u,pdf17]{pdfx}

\title{BMC}
\subtitle{Pret\ldots}
\author{me}

\usepackage{hyperref}
\usepackage{hyperxmp}

\hypersetup{
    pdftitle={\@title},
    pdfauthor={\@author},
    pdfcreator=pdfLaTeX,
    pdfproducer={\@author},
    pdfapart=3, % need hyperxmp for this
    pdfaconformance=U % need hyperxmp for this
}

\begin{document}

Hello

\end{document}

Answer 1

I don't know anything about hyperxmp, but for sure pdfx package loads xmpincl to handle the expected XMP metadata. Your problem could arise from a slight syntax confusion.

1. Your approach

\hypersetup{
    pdftitle={\@title},
    pdfauthor={\@author},
    pdfcreator=pdfLaTeX,
    pdfproducer={\@author},
}

should work, as long as :

• you have loaded hyperref
• you don't have loaded pdfx (see pdfx manual page 17)
• you did'nt use \maketitle which by default empties both \@title and \@author

A MWE :

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{blindtext} % for example text only
\title{A simple title}
\author{A cute author}
\usepackage{hyperref}
\makeatletter
\hypersetup{
    pdftitle={\@title},
    pdfauthor={\@author},
    pdfcreator={pdfLaTeX with hyperref},
    pdfproducer={\@author},
    pdfsubject={Some answer about metadata},
    pdfkeywords={LateX  hyperref},
}
\makeatother
\begin{document}
\blindtext
\end{document}

and the meta data shown in PDF-Xchange and Adobe Reader:

. 2. Another option, without hyperref , using pdfLaTeX's command \pdfinfo, used as:

   \pdfinfo {   
      /Title (\@title)
      /Author (\@author)
      /Subject (\@suject)
      /Keywords (\@keywords) 
   }

The MWE :

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{blindtext}
\title{A simple title}
\author{A cute author}
%\usepackage{hyperref}
\makeatletter
\pdfinfo {   
          /Title (\@title)
          /Author (\@author)
          /Subject (Some answer about metadata)
          /Keywords (LateX  hyperref) 
       }
\makeatother
\begin{document}
\blindtext
\end{document}

and the result:

3. if you load pdfx, the metadata set relies on the \jobname.xmpdata file which could look as (see pdfx manual page 6):

\Title{Baking through the ages}
\Author{A. Baker\sep C. Kneader}
\Language{en-GB}
\Keywords{cookies\sep muffins\sep cakes}
\Publisher{Baking International}
\CoverDisplayDate{1er\ avril\ 1999}
\CoverDate{1999-04-01}

and as said in 1., \hypersetup method is disabled.

A third MWE :

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{blindtext}
\usepackage[a-3b,pdf17]{pdfx}
\title{A simple title}
\author{A cute author}
%\usepackage{hyperref}
\begin{filecontents*}{\jobname .xmpdata}
\Title{Another simple title}
\Author{A cute author}
\Subject{Some answer about metadata}
\Keywords{LateX \sep hyperref} 
\end{filecontents*}
\begin{document}
\blindtext
\end{document}

and its result:

Please notice that:

• I used pdfa-3b as pdfa-3u is not suitable according to @UlrikeFischer answer
• In the 3rd scheme (pdfx) the title ,is the one written in the .xmpdata, independently of \title in the main document
• The keywords creator, producer and others of the same kind are usually automatically set by pdflatex and pdfx, and could require much more effort if you really want to customize them.

Answer 2

pdfx as of March 2020 uses xmpincl which is incompatible with hyperxmp. But you probably don't need pdfx. Hyperxmp is the more elegant way to deal with metadata since it integrates seamlessly with hyperref and \maketitle and does not require external files. It works both with PDF/A-1b and PDF/A-3u.

%\pdfobjcompresslevel=0 %uncomment for Texlive
\documentclass{scrartcl}

\usepackage[pdfa]{hyperref}
\usepackage{hyperxmp}
\usepackage{mmap} %only needed for pdfTeX

\title{BMC}
\subtitle{Pret\ldots}
\author{me}

\hypersetup{%
    pdfapart=1,
    pdfaconformance=b
}

\immediate\pdfobj stream attr{/N 3} file{sRGB.icc}
\pdfcatalog{%
  /OutputIntents [
    <<
      /Type /OutputIntent
      /S /GTS_PDFA1
      /DestOutputProfile \the\pdflastobj\space 0 R
      /OutputConditionIdentifier (sRGB)
      /Info (sRGB)
    >>
  ]
}

\begin{document}

lorem ipsum

\end{document}

Answer 3

Yes with solution 1 and 2, ie without pdfx you can use \@title \@author and \@date. Provided you do it before \maketitle, or patch it to avoid erasure.

My answer was related to solution 3, as a macro in a filecontents environment will be written verbatim in the file. So you will need a specific \write with small problems of encoding if you use letters out of the 128 ASCII range.