You can, however, stack the Alex on a strong table or another piece of furniture that can hold the weight.

The very last page has a picture of stacked Alexes with a big X through the picture telling you in no uncertain terms that you cannot stack these drawers. If you want to see or need the assembly manual, just click here. One unit is made to bear the weight of the contents only and not the weight of another set of drawers. According to the assembly manual no you cannot stack Ikea Alex drawers.