a quick search on google for duplicity subtitles got me here:
http://www.subtitlesource.org/release/25161/Duplicity%5B2009%5DDvDrip%5BEng%5D-FXG
choose your language if available and download the subtitle file. open the movie with VLC, click the menu: Video > Subtitles Track > Open file
Then open the file you just downloaded
This should put the subtitles over the movie.
If the subtitles are not lined up correctly, click the tools menu, then click "track syncronization" here you can advance or delay the speed of the subtitles so that it lines up properly.
Hope this helps,
Sean