in general OSGi is suitable for a lot of applications - not only entire frameworks. The advantages you gain from using OSGi in my opinion depend on your knowledge and "programming style". Many developers don't care about modularity and object oriented design and architecture. In this case you probably won't see any advantages. If you're interested to create a modular application OSGi definitely helps you to manage modules and keep a clear design and architecture. Plus all the other little nice features of OSGi of course, like replacing "modules" at runtime etc.
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com