When defining the settings for your content, one of the options is the download priority.
There are 3 possibilities:
Low - manual download: The user needs to tap the publication manually to download or update the publication.
Medium - pushed when wifi: The publication will automatically download or update when the tablet has a Wifi connection.
High - pushed on any connection: The publication will automatically download or update whenever the tablet has a connection, wifi - 3G - 4G.