What is the issue?
PDF/UA > Basic requirements > Embedded Files > "F" and "UF" entries in file specifications > "F" or "UF" key missing in file specification
What does it mean?
It is a very special issue. It could be related to an embedded file, a link to an external file, a launch file action, a submit form action, import form data action and so on.
It is not easy to locate it in the document, because in a lot of cases it is not caused by an attachment but by annotations like links for example.
How to fix it?
Currently there is no tool in axesPDF available to fix this issue.
Related checkpoint
Matterhorn Protocol (PDF/UA)
Checkpoint 21: Embedded Files
21-001 The file specification dictionary for an embedded file does not contain F and UF keys - No rules (machine testable)
Read more: Matterhorn Protocol - PDF/UA translated into checkpoints