The disk is full trying to write to Macintosh HD.

The disk is full trying to write to Macintosh HD. Free some space on this drive, or save the document on another disk.

Try one or more of the following:
*Close any unneeded documents, programs, and windows.
*Save the current document on another disk.

If you run into this error you might need to check this error first:
Word is unable to save the AutoRecover file in the location you have specified.