The whole story started when I tried to sign a LibreOffice document. When you belive the internet, document signing is inbuilt into LibreOffice.
Manuscripts for scientific peer-review are delivered as PDF files. Thus it appears most natural to comment the PDF file itself instead of submitting the comments as a separate text (file).
I reinstalled Acrobat 5 to run it under wine. It didn't work. The reason appeared to be again a plugin: DocBox.api. After removing it everything went smoothly. Already before (using RedHat 9) I have had trouble with a Acrobat plugin (it was WebPDF.api at that time). Most manipulation of pdf files can be easily done with Linux tools, but one thing is tricky: cropping already existing pdf files. That's why I need Acrobat.