Hi, rwasham, I’ve not played with a PM3 LW or otherwise but perhaps this may help as the principle applies to all folders, I think (?).
Back all screws off including the pivot but not all the way. With the knife folded closed you’ll be able to push the blade or flex the handle to centre it. Tighten the pivot screw all the way without stripping it and push the blade or flex the handle if you have to, to ensure it’s centred with only the pivot screw tight.
Now, carefully just nip the screw closest the pivot. Don’t tighten it all the way but you’ll want it firm. Check the blade is centred. If it’s moved don’t push the blade. Flex the handle to centre it. Nip the next screw closest to the pivot as with the first one. Check your blade is centred and flex the handle again if need be, as before to centre it. Move to the next screw and do the same till you have all the screws nipped firm and your blade centred.
Go back to the screw closest the pivot and screw it down tight, careful not to strip it. Check the blade’s still centred. It shouldn’t have moved. If it has, don’t back the screw off. Flex the handle like before. Move to the next screw and do the same and the next till all screws are tight and the blade is centred.
Back the pivot screw off just enough to roll the blade open with your thumb a few times. It should still be centred. Adjust your pivot to your liking and give the blade a few solid flicks so the tang slams the stop pin. All things being equal your blade shouldn’t have move off centre and your done.
Hope this helps and do let us know how it all goes.