AFAIK there is no way for a correct translation. But it possible to generate a usefull PADS netlist from within Protel so if you move SCH just to do layout in PADS the you can still do it.
With netlist in PPCB and match with all decals it may be possible to reverse engineer into Powerlogic but never tried this myself.
I also agree with that there is no way to complete this task-convert protel schmatic to PADS schematic. Except there is a special software, buy it will cost too much, and no company like to do it. After all, drawing a new schematic is not as difficult as drawing a PCB.