Assumed Dan would ace these questions, I'm not terribly familiar with Arty stuff (and can't see the uploaded docs). I believe PL is Privilege Leave, days of leave 'earned' like vacation days based on time in service. This is standard leave, differentiated from various special leaves (embarkation leave, farm leave, compassionate leave, etc.). He would almost certainly have been away from his unit at this time. What unit was he on the strength of in Oct 42? It's not unheard of for guys working with a unit but not officially on their strength to appear in these photos.
Another thought, did you obtain the standard genealogical package of his docs from LAC? If you don't already have something, you might request his complete file in hopes of finding records of a Court of Inquiry into the circumstances of his injury that might provide some helpful details. The complete file will cost extra $ and give you lots of fairly useless stuff like dental records, etc., but might be an avenue worth exhausting. CoI records are often found in the personnel files of those involved. Only caveat would be that as they were in action at the time, it's possible this didn't happen. Most CoI's I have seen have been from training in the UK, though I have seen a couple from the field.