I reckon PM stands for "pick me", as in "pick me, Flapper".
Flapper was a fixture on Channel 9 in Perth back in the 1980's on things like Saturday morning kids shows. I think he used to appear with Humphrey B. Bear.
Anyone that grew up in Perth in the 1970's and 1980's would probably be familiar with Flapper. Saying "Pick me, Flapper", was a common response to any question.
For instance, if you were at the bar in Claremont on a Friday night getting a round of drinks during happy hour, and you yelled "Who needs a drink?", the response would be a chorus of drunks shouting, "Pick me, Flapper".
It was also a common response in our Regiment when a call went up for volunteers. If an NCO went, "Right you scaly toads, I need two men to go into town and pick up some goffas", there'd be a chorus of "Pick me, Flapper" - which was tolerated, so long as you were out in the sticks, the RSM was not within earshot, and you'd served enough time to no longer be a new guy.
So that's where the "PM" on Rudd's jacket came from - a West Australian with a sense of humour.