Connect your iPad to your computer and select it from the top-right button in iTunes.
Open the "Apps" tab, scroll down to File Sharing, and choose SoundNote from the list. You can save your SoundNote files from here. Follow the same procedure to load them back into your iPad later. Note, if you're using Windows, you may have to zip the .soundnote files before iTunes will accept them.
Drawn lines can be moved and deleted individually or as a group. Tap a line to select it, or tap twice to select an individual stroke. From there, you can drag it to wherever you want, or tap "Delete" to get rid of it. Use two fingers to zoom and scroll.