After describing a few of the ways you can convert .docx files to .doc format, readers sent in more suggestions. One of the best: use the command-line utility textutil. In the Finder, navigate to the location of the .docx file you wish to convert. (This tip will also work for .txt, .html, .rtf, .rtfd, .wordml, .odt, and .webarchive files.) Open a Terminal window and enter textutil -convert doc, and then drag the file you want to convert from the Finder to the Terminal command line. A converted copy of the file – myFile.doc – should appear in the same folder as the original.
If you need to do this a lot, you can deploy textutil as a service. Open up Automator and select the Service template. Set Service Receives Selected to Files Or Folders, and set In to Finder. Next, drag Run Shell Script from the Utilities section of the Actions library into the pane on the right. Set the Pass Input drop-down menu to As Arguments. Next to do in the second line of the text box, enter textutil -convert doc “$@”. Save the service with a name you like – Convert To .Doc for example. When you next Control-click on a file in the Finder, you’ll have a Convert To .Doc option in the context menu.