For each PDF/A-1 validation issue we try to explain what it means and, if possible how to resolve it. For a more technical explanation of the issue we quote the related section of the ISO 19005-1 PDF/A Specification.
Embedded files and external dependencies are not allowed within a PDF/A file.
How can I fix it?
Open your PDF file in Solid PDF Tools and then File | Save As PDF/A. This will remove any embedded and external dependencies in your PDF/A file.
6.1.11 - ISO 19005-1 PDF/A Specification:
A file specification dictionary, as defined in PDF Reference 3.10.2, shall not contain the EF key. A file’s name dictionary, as defined in PDF Reference 3.6.3, shall not contain the EmbeddedFiles key.
NOTE: These keys are used to encapsulate files containing arbitrary content within a PDF file. The explicit prohibition of these keys has the implicit effect of disallowing embedded files that can create external dependencies and complicate preservation efforts.