At the very end of the level - there are 9 files you need to open. I have created the map below to show the order. Note that the 9th document isn't accessible until you open the first 8.
X - wall or cabinet
O - walkable area
Number - order to open in
XXX(8)OOO(5)XXX(6)OOO(2)XXX
X(9)OOOOOOOOOOOOOOXXX
XXX(7)OOO(3)XXX(4)OOO(1)XXX
XXOOOOOOOOOOOOOOOXXX
(Entry Door)