Thanks for the reply,
"Document properties" tells me the file was created by: Adobe InDesign CS4 6.0.7
Since I do not have the original Font (as Irosenth suggested) an invalid/wrong "ToUnicode CMap" seems likely.
I suppose there is no way to remove, fix, ignore or detect the ToUnicode CMap issue within a given Font, besides refrying or upgrading InDesign?
It seems strange to me that the refry (Acrobat -> Save As) process discards the ToUnicode CMap and on the other hand, when viewing, Acrobat seems to "repect" the ToUnicode CMap.
Kind regards,
Robert