You can get it here if you want:
http://www.15mm.co.uk/collections/laserburn-15mm-science-fiction
I loved Laserburn too. It was the skirmish game I grew up on. I still have a copy of the rules but not the miniatures. I've been tempted to go and start a new collection but so far I have somehow managed to resist the temptation.
I'll also add one more voice to the PDF bandwagon.
Although very much before my time, i'm really interested in starting up laserburn as a way to use my 15mm scratchbuilds.
I hope it sees a bit of a revival with the rise of oldhammer and more retro games becoming popular again.