Working on a large project with language barriers

Our University is working with another University in South America on a single development project. While some of their professors have a good grasp on English, most of them speak only Spanish.

We've developed a fairly large design document and we're currently working on technical documentation parallel to development. My question is what's the most efficient way of managing these documents? Ideally I would like to create a Word document that includes both an English and Spanish translation in the same document (to keep both documents in sync rather than trying to manage two documents).

Is this possible? Are there any tools available to help multiple developers of different languages work on the same project?

I'd say that this is where UML/Visio would come in handy. While translations will help when describing whatever's in the document, you could (theoretically) assume that if you guys create proper UML diagrams then both parties can, together, curse and moan at the incomprehensibility of the diagrams. (I mean, they should be able to understand most of it by such diagrams, because less text being translated may decrease the chance of misinterpretation or error)