Unfortunately this did not work as I got a 'permission denied' message. Here is one example, though I tried for several different files, including a .docx file in my Desktop folder.
732L-114016-M:~ ckirkby$ mdimport -d4
Usage: mdimport [OPTION] path
-d debugLevel Integer between 1-4
-g plugin Import files using the listed plugin, rather than the system installed plugins.
-p Print out performance information gathered during the run
-A Print out the list of all of the attributes and exit
-X Print out the schema file and exit
-L Print out the List of plugins that we are going to use and exit
-r Ask the server to reimport files for UTIs claimed by the listed plugin.
-n Don't send the imported attributes to the data store.
-o path Write the imported attributes to a file, instead of sending them to the server.
732L-114016-M:~ ckirkby$ /Users/ckirkby/Dropbox/Library/2012\ -\ Ballantyne\ -\ Webs\ of\ Empire.docx
-bash: /Users/ckirkby/Dropbox/Library/2012 - Ballantyne - Webs of Empire.docx: Permission denied