MusicReader
http://www.musicreader.net/I work on the files on the PC, and sync to the iPad.
I "print" pdf files (usually from Sibelius) using MusicReader supplied print driver, manage the files in MusicReader's library, annotate the sheet music and create playlists for each program. Images are crisp and clear, making it easy to read even on the small iPad screen.
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Graham, Korg Pa1000, Korg G1 Air, Countryman E6, Roland BA330, 2 x Roland CM-30, , Mackie SRM150