BUILT-IN WOLFRAM LANGUAGE SYMBOL
is an option for Cell that specifies whether a page break should be allowed within the group of cells if the notebook that contains the group is printed.
Create a notebook with several groups of cells, with page breaks allowed within a group:
This shows that the first page break splits a group between pages:
Create a notebook of several cell groups, with page breaks not allowed within any group:
Now the page breaks can only occur between groups: