smart document implementation and add-in functionality in same instance of dll

[Maarjakas]

Is it possible to have both smart document and add-in functionality in
same dll?
I have Word add-in project where I also have class that implements
ISmartDocument interface. The result is one dll, BUT add-in and smart
document uses different instances of that dll. Is it possible to
achieve situation where Word use only one instance of this dll? (smart
document could use the dll that is created by add-in, when Word opened
or ...?)