A method for digitally signing, in a shared manner, a digital document by a plurality of users (4', 4"), comprising the following steps: - A) preparing a remote processor provided with a database containing authentication information associated with users (4', 4") of the service; - B) associating a first mobile electronic device to a first user by storing identification information of the first electronic device in the database and storing association information regarding an association between the first mobile electronic device and the first user; - C) associating a second mobile electronic device to a second user (4") by storing identification information of the second electronic device in the database and storing association information regarding an association between the second mobile electronic device and the second user (4"); - D) preparing a digital document which must be digitally signed and displaying the digital document in a display of the first mobile electronic device; - E) starting a session for digitally signing the digital document comprising the following steps: - F) electronically transmitting first identification information of the first electronic device from the first electronic device to the remote processor; - G) checking the identity of the first user, on the basis of the first identification information, by interrogating the database; - H) electronically transmitting from the first mobile electronic device to the second mobile electronic device information designed to allow a display of the digital document on the second mobile electronic device; - L) electronically transmitting second identification information of the second electronic device from the second electronic device to the remote processor; - M) checking the identity of the second user (4"), on the basis of the second identification information, by interrogating the database; - N) electronically sending, in the case of a positive outcome of the identity checks, a notification of signature by the second user (4") to the first electronic device so as to complete the digital signature of the electronic document by the first and the second user (4', 4"). - A) preparing a remote processor provided with a database containing authentication information associated with users (4', 4") of the service; - B) associating a first mobile electronic device to a first user by storing identification information of the first electronic device in the database and storing association information regarding an association between the first mobile electronic device and the first user; - C) associating a second mobile electronic device to a second user (4") by storing identification information of the second electronic device in the database and storing association information regarding an association between the second mobile electronic device and the second user (4"); - D) preparing a digital document which must be digitally signed and displaying the digital document in a display of the first mobile electronic device; - E) starting a session for digitally signing the digital document comprising the following steps: - F) electronically transmitting first identification information of the first electronic device from the first electronic device to the remote processor; - G) checking the identity of the first user, on the basis of the first identification information, by interrogating the database; - H) electronically transmitting from the first mobile electronic device to the second mobile electronic device information designed to allow a display of the digital document on the second mobile electronic device; - L) electronically transmitting second identification information of the second electronic device from the second electronic device to the remote processor; - M) checking the identity of the second user (4"), on the basis of the second identification information, by interrogating the database; - N) electronically sending, in the case of a positive outcome of the identity checks, a notification of signature by the second user (4") to the first electronic device so as to complete the digital signature of the electronic document by the first and the second user (4', 4").