There doesn't seem to exist any direct way how .iwa files could be converted to anything else, including .doc files via potential iwa to doc conversion. It appears that .iwa files are found inside compressed documents from iWorks (.pages, .numbers etc.) and replaced the previously used XMLs that were utilized for the document structure. If you want to convert your document, you will need to convert it as whole, not just a part from inside, something like pages to doc conversion or similar.
Some source claim that it might possible to somehow decode the .iwa files (they feature Snappy compression) and rebuild some kind of "old" version of iWorks documents, but that seems like highly unreliably and somewhat complicated way to achieve iwa to doc conversion.Open IWA file Open DOC file
Mobile version of popular word processor from Apple
A word processor and layout tool marketed by Apple