You must save the macro in the document. When you create it, you must select
the document as the location to save it (by default, macros are saved in
Normal.dot). And then of course others who use it will have to enable the
macro if challenged (and to even given the option, they must have Macro
Security set to Medium rather than High or Very High). A better solution in
some cases is a template containing the macro, installed the User Templates
folder if a document template is required or in Word's Startup folder (as a
global template) if only the macro is required; these are "trusted
locations," so macros will not be challenged provided users' Macro Security
is set to "Trust all installed templates and add-ins.