If you are going to use some form of electronic storage, then you must conform to the U.S. Citizenship and Immigration Services (USCIS) requirements for using an electronic storage system for Form I-9. Merely putting the form in the cloud or on a computer is not sufficient.
Consult the USCIS’s Handbook for Employers M-274: Guidance for Completing Form I-9 (Employment Eligibility Verification Form), using the Table of Contents for the section on "Retaining Form I-9."
Read more on "Electronic Storage of Form I-9" on Completing the Form I-9 in the HR Library.