Question Mark in titles (file names)

When I save a document. I can’t include a question mark.

If you mean “in file names” instead of “in titles”, then it’s your operating system limitation. E.g., in Windows, it is illegal to include question marks (and some other characters) in file names.

There is a lengthy list of filename limitations on Wikipedia; as @mikekaganski mentions, nearly all the Microsoft file systems do not allow ? in the file name.