This works in the command prompt(in one line) :
cd C:\Program Files (x86)\LibreOffice 4\program &&
"C:\Program Files (x86)\LibreOffice 4\program\python.exe" unoconv -f pdf d:\class1.doc
but when it comes to do the same in PHP's exec() nothing happens - neither message nor any file, probably due to a syntax error :
echo exec('cd C:\\Program Files (x86)\\LibreOffice 4\\program &&
"C:\\Program Files (x86)\\LibreOffice 4\\program\\python.exe" unoconv -f pdf d:\\class1.doc');