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 does not allow malformed streams, keys that point to external content or other external file dependencies.
How can I fix it?
Use Solid PDF Tools to adjust the PDF File structure. It will remove prohibited keys, adjust stream delimiters and stream length mismatches to create a PDF/A compliant file.
6.1.7 - ISO 19005-1 PDF/A Specification:
The stream keyword shall be followed either by a CARRIAGE RETURN (0Dh) and LINE FEED (0Ah) character sequence or by a single LINE FEED character. The endstream keyword shall be preceded by an EOL marker.
The value of the Length key specified in the stream dictionary shall match the number of bytes in the file following the LINE FEED character after the stream keyword and preceding the EOL marker before the endstream keyword.
NOTE 1: These requirements remove potential ambiguity regarding the ending of stream content. A stream object dictionary shall not contain the F, FFilter, or FDecodeParms keys.
NOTE 2: These keys are used to point to document content external to the file. The explicit prohibition of these keys has the implicit effect of disallowing external content that can create external dependencies and complicate preservation efforts.