I encounter this problem in the moment of enumeration the existing opened files, before sending them to my system. Later, if these files were coming from cloud and i get "Acrobat.com: myFile.pdf" (see the initial discussion), I applied PDDocCopyToFile() as in the example from the top to generate a temporary file into the Windows\Temp path, but this file should have the correct name.
The only challenge is how to get that correct "unicode" file name.