iTextSharp .Net DLL included as “embedded resource

问题:

I followed the instructions at VB.NET embedded DLL in another DLL as embedded resource? to implement three dlls as embedded resource in my VB.NET project. Two dlls are made with 100% managed code, they are loaded at runtime and work perfectly, however only "iTextSharp.dll" (http://sourceforge.net/projects/itextsharp/) does not load when requested from the assembly, besides I don't know if it's a managed DLL or not. Any suggestion will be very appreciated.