[EN] Compressed metadata stream on document or on object level

Description

Some PDF-based ISO standards require that metadata dictionaries must not contain filter keys, which essentially means they must be embedded in plain text.

PDF documents often contain metadata that provides additional information about the content and structure of the document, such as author, creation date, software used, and much more. This metadata can exist in either an uncompressed or compressed form.

If the metadata is compressed at the document or object level, it can lead to processing issues, particularly regarding accessibility or the ability to search and extract metadata. Compressed metadata is often useful for efficiency and storage optimization but can cause problems with displaying or editing the document if not handled properly.

Common Causes

Optimization of Metadata: Some software tools or PDF creation processes compress metadata to reduce file size and optimize performance, especially in very large PDF documents.

Use of Compression by Third-Party Software: Sometimes, metadata is compressed by tools or libraries that do not fully support PDF metadata.

Automated PDF Creation: During automated PDF creation (e.g., via scripts or non-specialized software), metadata may be unintentionally compressed without the user intending it.

Incorrect Application of Compression Algorithms: Compression methods such as Flate or ZIP are sometimes applied to metadata to minimize file size; however, this results in the metadata no longer being in its uncompressed state, making it difficult to access for programs that do not support compression.

Suggested Solutions

Workaround – Using a Different PDF/X Standard

This check is specific to PDF/X-4 data. The PDF/X-1a and PDF/X-3 standards do not impose requirements regarding compression of metadata at the document or object level and generally require less metadata. Converting embedded PDF objects to these standards and exporting as PDF/X-3 or PDF/X-1a can help avoid this error message.

Disabling Compression in the Software

Check the export settings in the software used to create the PDF. Many applications, such as Adobe Acrobat, Illustrator, or InDesign, offer the option to disable metadata compression.

Make sure that metadata is exported uncompressed, especially if the PDF is intended for archiving or for metadata exchange with other systems. To do this, go to the export options of the software and look for a setting related to metadata compression or the compression of the entire document content.

Using Preflight Tools

Open the PDF in Adobe Acrobat Pro or another preflight tool and run a preflight check. The preflight check will indicate whether and which metadata is compressed, and will give you the option to optimize the file. Many preflight tools offer a specific option to remove compression from metadata. If the file is being prepared for exchange or archiving, it is recommended to use this option.

Manual Review and Correction

Open the document’s XMP metadata. You can do this using Adobe Acrobat or another application that allows access to XMP metadata.

Remove or decompress the metadata. In some cases, it may help to delete the XMP data entirely and recreate the metadata from scratch.

Automatic Repair via Optimization

PDF optimization tools such as Adobe Acrobat Pro offer a feature called “Save as Optimized PDF.” This function can be used to decompress compressed metadata, optimize the file, and reduce its complexity.

Ghostscript and similar software products also provide automated repair functions that can remove compression.