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Including Custom Metadata Structures in PDF

Many industries and organizations define various metadata schemes beyond those specified in ISO standards for PDF technology.

In PDF, all such third-party schemes are “custom metadata”, often existing as manifest files in various serialization formats supporting existing complex workflows and systems. Organizations leveraging these metadata in the PDF context can benefit from guidance regarding appropriate method(s) for including their custom metadata in PDF documents, enabling smoother and more efficient workflows and avoiding “sidecar files” or less user-friendly ZIP archive-based solutions.

This Application Note presents methods for incorporating custom metadata structures into PDF files. It  provides recommendations and guidance to assist organizations in selecting the most suitable mechanism(s) for storing their custom metadata manifests in PDF documents, consistent with ISO standards for PDF.

A basic understanding of PDF is assumed.

NOTE: This Application Note focuses on larger custom metadata schemes and thus does not provide detailed advice on other mechanisms more appropriate for lightweight or small custom metadata data points.

Industry metadata extensions

Third-party XMP

Adobe maintains a list of various standards initiatives using XMP as their framework of choice for metadata. The extensibility of XMP allows standards to be carried throughout the workflow. 

EDItEUR ONIX

EDItEUR has released an ONIX application note on embedding ONIX XML metadata within a PDF. Developed in collaboration with the PDF Association, this note is designed for publishers who wish to include information for use with archiving and preservation, and especially (in the context of recent EU regulatory changes) to record the accessibility status of the PDF. Download the ONIX application note from EdItEUR.

Comments or additions?

Technical questions about this Application Note are most effectively addressed by the PDF TWG. If you are not a member of the PDF Association but wish to offer a comment on this document or register support for custom metadata, please write to info@pdfa.org.

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