LibreOffice (using Linux)

1. using Linux a certificate manager like "kleopatra", "seahorse", "gpa" or "kgpg" is needed

   

2. . open libreoffice (e.g. "Writer" for text document)
   
    

3. create the document (do not forget to save before going on with signing)
   
   

4. the signing menu opens now
   
   
   
   

5. now the window where you can choose the certificate/keypair opens
   
   

6. the windows in the baqckground ca be closed using <Esc>

7. now the certificates are show for which valid information are stored in "kleopatra" (e.g. private key)
   

8. select the wanted certificate/keypair and add a short description if wanted/needed
   
   

9. and sign the document as final step
   
   

10. "Close" this last window at the end
    
    

11. the document shall now show a valid signature
    
    

12. close the document

    Important note - do not save the file as the signature will be lost if doing so