Hello,
I agree with Sherry and Mark.
Often the simple scanning & midi output tool can do a reasonable job, according to Sherry's experience.
If you need more functionality, then Musitek's Smartscore 3.x
at a higher price delivers you more, I have done some work with it.
http://www.musitek.com/
But your paper music must be of high quality (contrast and no damages)
Cheers Jaap