Where to find parchments?

[Tartan Waft Esquire]

I have 5 so far and was wandering if they drop from specific places and/or mobs?

[Fozzie]

As far as my experience goes, that really depends on the specific scroll. Some of them are bound to a certain enemy type, like the one from the teenage Maenad. Others seem to be completely random, I had the one about the magician ("The Amazing... whossname") drop at least in two different acts.

[Shadow Blade]

The only one I have ever gotten is the Turtle one. Got it from one of the aunoran (Frog things in act IV)