WITH 
cte1 AS ( SELECT *, ROW_NUMBER() OVER (PARTITION BY DocumentNumber ORDER BY id) rn
          FROM in_fileindex_additionaly ),
cte2 AS ( SELECT *, ROW_NUMBER() OVER (PARTITION BY DocumentNumber ORDER BY id) rn
          FROM in_fileindex_applicability ),
cte3 AS ( SELECT GREATEST((SELECT MAX(rn) FROM cte1), (SELECT MAX(rn) FROM cte2)) rn )
SELECT *
FROM in_fileindex_main main
CROSS JOIN cte3
LEFT JOIN cte1 USING (DocumentNumber, rn)
LEFT JOIN cte2 USING (DocumentNumber, rn)
WHERE COALESCE(cte1.DocumentNumber, cte2.DocumentNumber) IS NOT NULL
ORDER BY DocumentNumber, rn

WITH cte1 AS (...) SELECT * FROM cte1

WITH cte1 AS (...), cte2 AS (...) SELECT * FROM cte2