Error in reading a pdf

[sinus]

Hello
To be honest, I have this message since a long time on every pdf, but it does not any harm.  (I hope).
Now I am curious, does anybody know, what this means?

See the attachement, on every pdf I have a exclamation-sign and if I click on it, an error - code.

The pdfs are mostly created by Print & Design inside IMatch, but the same sign is also on other sources.

[Mario]

This message comes from ExifTool. It does not understand the metadata in your PDF files. I have never seen this message myself, though.

[sinus]

This message comes from ExifTool. It does not understand the metadata in your PDF files. I have never seen this message myself, though.

Thanks, Mario

not so important, I will have a closer look, when I have more time. 

[Mario]

Send me one of the files so I can have a closer look.