(Verzeihung dass ich auf English antworte.)
Can your application read registry entries? Key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\AcroRd32.exe contains the full path to the currently installed Reader.
I don't know of any environment variable that contains the path to AcroRd32.exe
i'm not sure... because i do not know how to write the entries
in the first line, i've to write the program call, in 2nd line the file name
If that program call is to be hard-coded, then I wouldn't know how to do that. (Also I don't know what programming language you use.)
Perhaps you could create an environment variable yourself that points to the AcroRd32.exe file? Or you could put the path to the executable into the %PATH% environment variable, so you just call AcroRd32.exe (without an explicit patch)?
Also, wait some 24 hours or so; someone else may have a better idea.