For Eudemon warehouse, go to your cq_npc and look for entries with the data3 parameter of 10. For each page you want, add 5 to that number.
For example, if you want 10 pages, change the number to 50. (10[Original 2 Pages] + 5[1 more page] + 5 + 5 + 5 + 5 + 5 + 5 + 5 = 50spaces[10 pages])
Normal warehouse might work the same way; I haven't tinkered with it.