Documentation for HKL-2000
You can find an online PDF version of the manual covering mainly Denzo and Scalepack (the actual programs run by the HKL-2000 graphical interface) at the HKL2000 website*.
There is also a nice online manual for HKL-2000 on the HKL-2000 website.
*Please note, however, that the HKL manual is copyrighted and cannot be distributed without permission.