ZUGFeRD PDF is Invalid

When validating a ZUGFeRD document that has been produced by FORNAV, you sometimes might experience that the PDF itself (and not the electronic document attached to it) is invalid.

What is happening in this instance is that the ZUGFeRD validator validates that the PDF is compliant with the PDFA-3 standard and, even though the PDF is 100% readable, it reports missing metadata.(This metadata is only necessary in a far future, where Windows and MacOS does not exist anymore, and all the metadata needs to be embedded in the PDF in order to 100% reproduce the visual look of the PDF.)

In this case, the problem is that a watermark, logo, or picture is based on a PDF that is not PDFA-3 compliant and therefore does not contain the necessary metadata.

To check if this is the case, you can simply open the PDF in a text editor and search for “Device”. If you have a ColorSpace called DeviceCMYK, it is likely that this is what caused the problem:

To fix this issue, you can use a PDF editor (for example, Adobe) and modify the PDF containing CMYK to instead use RGB. However, since this issue does not affect the readability of the PDF or the electronic document attached to it, it is easier just to live with the issue and dismiss the error message.