Donaldson is the second graduate from Livingston's youth programme to head from Scotland to England this month.
Stefan Scougall moved to League 1 Sheffield United last Friday, and although Livingston boss John McGlynn was disappointed at losing both players, he remains pragmatic.
McGlynn said: "Coll's worked hard to move his way up through the youth ranks here, so it's always a sad occasion when one of our own moves on.
"But like Scougall, Coll's earned his crack at English football, and we will never stand in the way of any ambitious young players.
"I'm in the market for signing a replacement and hope to have more news on that soon."