Both DOC and SDW are a bit older, yet still used document formats and as such can be converted between each other. This can typically be done in various word processors, especially those based on OpenDocument schema.
Convert Microsoft Word document (prior version 2007) to OpenOffice.org text document.
We have found 3 software records in our database eligible for .doc to .sdw file format conversion.
Apple macOS / Mac OS X software - convert doc to sdw on OS X
A full-featured set of office applications for Mac OS X
Convert from doc file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned doc to sdw. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Multiplatform software - convert doc to sdw on any platform
Word processor and text editor from OpenOffice.org suite
Full-featured word processing and desktop publishing tool from LibreOffice suite