The new Offline documents module have a new feature called ‘favourite documents’. A document in the traditional app will only be visible in the offline document library if only it is made a favourite document.
A document can be made favourite by two methods,
Favourites made by self - These documents have to made favourite by the user and those will only be visible for self. Any self important documents can be listed as examples for this type.
Mandatory favourites - These documents were made favourite by any person who have ‘Write’ access to the folder. If you want your users to mandatory store a documents in their PWA, you can make a document ‘Mandatory favourite’.