Hi Azertok,
There is no 'formula' in Word that would do this.
You could use a macro to insert the paragraph break at the end of every second line, but the complexity of such a proacedure would
depend on your document's layout, including how one should treat any existing paragraph breaks - especially those that result in a
paragraph having an odd number of lines. Then there's the question of what to do with any tables in the document, etc, etc.