Do NOT just write text over your videos, use a subtitle tool to be able to give the subtitles to partners for translation in .SRT format.  Below you find instructions on how to use various subtitle tools… 

How to add closed captions/subtitles with YouTube (automatic translation that you can edit and download) 

Subtitles in Premiere Pro

Subtitles in Movie Maker

Subtitles in Subtitle horse (online tool)