Thanks for your inquiry. It is quite difficult to answer such questions because CPU performance and memory usage all depend on complexity and size of the documents you are loading/generating. In terms of memory, Aspose.Words does not have any limitations. Usually, Aspose.Words needs 10 times more memory than the original document size to build a DOM in the memory.
Moreover, a document size on disk is usually smaller than document size in memory. There is no fixed relationship between disk size and memory size, it depends on the complexity of the document, formatting etc, but memory footprint will always be bigger than size on disk. If you have a document 1.7mb on disk and 12mb in memory it could be reasonable. It could be reasonable for some documents at some point in their life (remember garbage collector is always working etc).
Hope this answers your query. Please let us know if you have any more queries.