A polite phrase used to make a suggestion or invitation while leaving the choice to the listener; meaning 'if you don't mind' or 'if you'd like.'
もしよかったら、今度一緒に食事に行きませんか？
If you'd like, would you like to go out to eat together sometime?
資料をコピーしておくので、もしよかったらお持ちください。
I'll copy the materials, so please take one if you'd like.
もしよかったら、家まで送りますよ。
If you don't mind, I can give you a ride home.