SQL Server replication with masking columns

Using a sql server, I have to replicate the database 'source' to the 'target'. It will be a pull subscription, ran as agent on the target. Some of the columns will have to be masked, so not to be shown to users at the 'target'. > 1.) I know how to do masking, using alter table alter column command > 2.) I know to make sure the user on the 'target' is denied unmask permissions The question I have is such: The database on the 'source' existed for a long time, and the columns are currently not masked. Do I need to specifically run alter table alter column on every table/column I need it on ? before setting up the snapshot replication publication ? Or is there an option to mask specific columns at the time the snapshot is created ?