Of course it can, why not? The thing is your style may vary depending on the kind of writing, but words such as "actually" are not prohibited in any case, and will not be, no matter what some people say. Actually, replacing everything simple with longer, "smart" expressions, writing long, convoluted sentences etc. is a sign of bad style. There are specific guidelines in certain fields, however, depending on what you do (academic writing, journalism, technical documentation, legal documents, bureaucratic nonsense etc.)