var path = "/sdcard/Download/MyBill.pdf";
app.OpenFile( path,"application/pdf" );
There is nothing built in to DroidScript to parse pdf.
There are JavaScript pdf reader libraries available on github.
I expect some of them would be usable in DroidScript but I have not tested any.
It might be worth looking in npmjs to see if there is anything that can be browserified to make a plugin.