I have designed for both of Canada's official languages since 2001, and have had several opportunities to work with Spanish and Arabic also. Designing for multiple languages is a complex undertaking.
The french version of any text is almost always 1/3 longer than the english version. Spanish is shorter. Arabic has its own alphabet and reads from right to left. All languages have unique punctuation rules.
Add to these technical complexities the sensitivities of cross-cultural translation, and you have a serious challenge on your hands – and we love it!