The formation of Douglas Media marks Douglas' return to customer publishing after an accident last year left her unable to work for several months.
Douglas, a former Sunday Express editor, was with Conde Nast for five years and helped to develop Glamour's print and web editions.
She had previously been executive editor at Sunday Business, The Scotsman and Scotland on Sunday.
She said she was currently talking to several clients about publishing opportunities.
Miller, former commercial director at Conde Nast, was one of several high-profile departures as the company scaled back its customer publishing ambitions last year.