“pdfmark” is an experimental open source tool that allows you to add Crossref metadata to a PDF. You can add metadata to a PDF by passing the tool a pre-generated XMP file, or you can apply Crossref bibliographic metadata by passing the command a Crossref DOI as an argument. If you pass it a Crossref DOI, it will automatically lookup the metadata for that DOI using the Crossref OpenURL API, generate XMP from said metadata and apply it to the PDF.
Note that pdfmark is non-destructive. It will always generate a new PDF with the XMP added to it. Having said this, pdfmark does not re-linearize the resulting file. To re-linearized the PDF you can simply use ghostscript’s pdfopt command or any similar tool (e.g. Acrobat Pro).
“pdfmark” is open source. We have released it in order to encourage publishers and other content producers to start adding embedded bibliographic metadata to their PDFs.