You cannot play Knowledge cards for another person. So the card Lost Schema, which reduces the cost to build a component by one resource, cannot be played to let someone else pay one less resource when building a components.
That said, some knowledge cards benefit everyone, like Ancient Atlas (reduce all target numbers in one section by 1); anyone placing in the chosen section would benefit from the reduction of the target numbers.
Also, there are knowledge cards and a component that let you trade knowledge cards to another player (who can then play them).
Hope that helps!
Bleh, wish I had caught this before our first game tonight. Sharing Knowledge cards really did dampen the difficulty of the game and contributed to our (now tainted) win We had one player focusing almost solely on Knowledge cards for the rest of the table. A fun game nonetheless, but I expect it will be much more challenging next time around.