Situation is as follows: I'm a developer in some small IT company in Germany - started the job about 6 months ago. Work climate is great, everyone gets along very well with each other and behaviour among colleagues is very casual.
Now I've come by some presentation my boss made for one of our English-speaking customers - while it wasn't terrible, there were some noticeable mistakes that a native speaker might take as lack of professionalism/competence.
The question is now how do I best tell him that I want to proof-read those things to make the company as a whole look better? My main problems are firstly that it's, well, not my job but that of a consultant and secondly that I'm relatively new at the company and that he's twice my age and will probably doubt that I have a better grasp on the English language than he does.
So how do I point things like these out without sounding like a smart-ass?