This is the website for the Pakistan Game Fish Assoc. They have a forum and lot’s of info that might be helpful for him. Some fly fishers there he could hook up with, and group trips, and suggestions on where to go:
Official Website of The Pakistan Game Fish Association | PGFA
As far as flies, just a wild guess.... but I'm guessing if there's not a lot of fly fishing then patterns don't need to be too fancy. And maybe the flies should be easy to fish if he's a beginner
For fast flowing streams, coming out of the Himalayas:
high floating, easy to see dries like Royal Wulffs, Black Elk Hair Caddis in 14 and 16, Goddard Caddis 12, Grasshopper or unweighted Muddler Minnow 10
sub surface: Black Gnat Wet Fly 14, Bead Head Prince Nymph 12, Partridge and Peacock Soft Hackle 14
Surface: Parachute Adams 14 or Blue Wing Olive 16, and something light colored like a Light Cahill or Sulphur Comparadun in 16
Subsurface (some weighted, some not)
Hares Ear Nymph 14, Pheasant Tail Nymph 16, Partridge and Orange Soft Hackle 14
and for big trout in lakes and maybe even mahseer or snakeheads
Bead Head Wooly Bugger in black and/or olive 8, Black Marabou Muddler 6 or 4, White Zonker 6
Just guessing, but something like an assortment of the above might be a good place to start to cover a lot of different bases and offer some variety, and may catch him some fish insh'allah.
Good luck to him. It would be great to have him join the forum, would love to hear stories about his adventures over there.