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.
PDF/A requires device specific color output parameters to insure that the document will render and output as close to the original colors as possible.
The document does not specify any output intent or the output intent in use is not correctly identified.
How can I fix it?
Use a PDF creation product that correctly identifies output intent. We recommend Solid PDF Creator Plus.
If you are working with a legacy document, simply open your PDF file in Solid PDF Tools and then File | Save As PDF/A. This will add or adjust output intents in your PDF/A file.
6.2.2 - ISO 19005-1 PDF/A Specification:
A conforming file may specify the colour characteristics of the device on which it is intended to be rendered by using a PDF/A-1 OutputIntent. A PDF/A-1 OutputIntent is an OutputIntent dictionary, as defined by PDF Reference 9.10.4, that is included in the file’s OutputIntents array and has GTS_PDFA1 as the value of its S key and a valid ICC profile stream as the value its DestOutputProfile key.
If a file's OutputIntents array contains more than one entry, then all entries that contain a DestOutputProfile key shall have as the value of that key the same indirect object, which shall be a valid ICC profile stream.