A family of Microsoft word processing software products for creating web, email, and print documents.
That is what templates are for. Create a document that has your preferred page numbering. Then save is as a template with a dotx ending. The, when you need a document with that page number format, choose File>New, select the template with that format and create a new document from it.
To do that for all new documents, open your Normal.dotm template, add page numbering in your preferred format, then save. Normal.dotm is the file used to create new blank documents automatically.
If you need further details, please start a new thread stating your operating system and Office version. That way you'll get better answers than tagging on to someone else's question.