The only thing to come to mind would be Greg Porter's EABA, which uses more advanced PDF functions. It does include fillable character sheets, as it happens, but they also do calculations for you.

The various EABA PDFs include things such as dice rollers built in and other bells and whistles, although there is a major drawback: the extras only really work properly on a desktop PDF reader. On a tablet, where they would arguably be more useful, PDF software is considerably more limited and struggles to handle them. I never did find an Android app capable of using them properly; things are better on iOS but even there you're pretty much restricted to PDF Expert.

I asked a programmer friend why there was such poor utilisation of these JavaScript functions in mobile PDF readers and he basically reacted with horror at the very idea 

Inexplicably duplicated reply I can't seem to delete.

BigJackBrass wrote:

The only thing to come to mind would be Greg Porter's EABA, which uses more advanced PDF functions. It does include fillable character sheets, as it happens, but they also do calculations for you.

The various EABA PDFs include things such as dice rollers built in and other bells and whistles, although there is a major drawback: the extras only really work properly on a desktop PDF reader. On a tablet, where they would arguably be more useful, PDF software is considerably more limited and struggles to handle them. I never did find an Android app capable of using them properly; things are better on iOS but even there you're pretty much restricted to PDF Expert.

I asked a programmer friend why there was such poor utilisation of these JavaScript functions in mobile PDF readers and he basically reacted with horror at the very idea 

Thanks!

Yeah, I do have the default on my .pdf readers set to "not allow scripting."
We can't have fun toys because the kids who laugh when they kick over snowmen and sand castles go on to make MS-Word and Excel malware... Sigh....