Hi,
About the only way I know of to communicate musically with any Apple product is to use an exported .mid file. However, that loses all the nice score formatting and such that you may have done in Musician or Composer.
If it's just a score that you want to just see the score, you can "print" a PDF copy of it and then put that on your iPad. A couple that I can recommend are CutePDF (free at
www.cutepdf.com) and PDF Creator (free/donation at
http://sourceforge.net/projects/pdfcreator/) After installing either of these, you can then use File/Print in any software program and "print" (save) a PDF copy. The bonus with PDF Creator is that it also allows you to save graphic files that you can insert in other documents.
Enjoy!
Sherry