On administrative computer where WebOffice author is installed, Windows .NET Framework 4.0 is required. The installation files of .NET Framework 4.0 Full package can be accessed through one of the following links. Keep in mind to choose the full installation (full package) when installing .NET Framework 4.0.
http://msdn.microsoft.com/en-us/library/vstudio/5a4x27ek(v=vs.100).aspx
http://www.microsoft.com/en-us/download/details.aspx?id=17718
http://www.microsoft.com/en-us/download/details.aspx?id=17851
Note: After having installed the .NET framework it is necessary to re-start the server.