Unfortunately the automatic generation of a spell sheet can take a very long time because it uses some functions in Adobe Acrobat that have a time-out event in them, meaning that Acrobat is waiting on itself constantly, slowing down the whole. This is not something I can change as far as I know. The amount of time it takes to generate depends on the amount of spells that will be put on the spell sheet and does not seem to be affected by the systems performance much (i.e. older systems and newer systems will run it just about as fast). Thus, it can easily take over an hour to generate a spell sheet that contains all the cleric spells.
If you are concerned that your Adobe Acrobat is frozen, simply take a look and see if the process is still using CPU (with Task Manager for example). If the program stays at 0% or close to 0% CPU usage, than it is probably frozen. If it still using your CPU, than you will have to wait a bit longer.