Noteshelf is described as 'Take beautiful handwritten notes or annotate PDFs on your iPad, and now even on your iPhone' and is an app in the Audio & Music category. There are more than 100 alternatives to Noteshelf for a variety of platforms, including Windows, iPhone, iPad, Android and Mac. The best alternative is Joplin. It's not free, so if you're looking for a free alternative, you could try Standard Notes or Microsoft OneNote. Other great apps like Noteshelf are CherryTree (Free, Open Source), NoteLedge (Paid), Zoho Notebook (Free Personal) and Trilium Notes (Free, Open Source).
Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, can be copied, tagged and modified either from the applications directly or from your own text editor.
Colorful & powerful sticky notes app for Windows & Phones. Set reminder alarms, attach them to any website or document, organize them using folders/tags, sync sticky notes between devices & send notes across LAN or to any contact across the globe.