It is acceptable to sign documents electronically, in the same way that a signature on a document that has been faxed is acceptable.
Where you must be careful is the method by which the signed document is served or delivered.
We cover the various methods allowed under the Residential Tenancies Act in our "Town Hall" material on serving notices, it is available here: http://landlordselfhelp.com/media/2016/01/TownHall_serving-doucments_public.pdf