If you have an Apple Pencil, I highly recommend “Concepts” [0]<p>I use it for general software design/planning like UI wireframes, flowcharts and various other things<p>[0] <a href="https://concepts.app" rel="nofollow">https://concepts.app</a>
Goodreader is an excellent PDF repository and reader if you have a large library (I’m a TTRPG gamer) although you can get by with iBooks.<p>I find Google Drive and Google Docs indispensable, but Notability is also excellent. The built in notes app is surprisingly capable though, so you might as well check it out.