http://www.folia.com/

From the makers of iAnnotate, Folia is an enhanced word processor. According to the developers, "We’ve explicitly designed Folia to move beyond these [traditional word processor] limitations with traditional links to richer connections. These connections not only allow you to link between documents, they also allow you to add markups and comments to the connected documents themselves. Each connection allows you to capture a unique perspective. These connections may seem simple, and in a way they are, but you’ll be amazed at what you can convey with such simple pieces." It seems to ingest PDFs, too.

I'm not keen on signing up for a word processor before I can test them out so if you don't mind - can you clarify what Folia is as a word processor? The video only shows an image being commented.

Must be some limit on new accounts -- I've attempted several times for days, with different email accounts, to get a login. The verification email never comes. There appears to be no way to test the application or see the interface without an account.

Sorry, haven't actually tried this one yet. I thought the ability to read in and annotate pdfs would appeal to some of the users here - not something I do very often.

Managed to finally arrange for an account. The app (Mac App Store version) has barely any features. Type text; headings; bullets; links between documents but not hyperlinks. No export, save, or print features at all. I assume this is intended just for collaboration (with others who have Folia accounts) and cross-platform note taking. It is not a hierarchical outliner. There is a screen buried in the account setup that makes it clear that there will be a subscription model with (perhaps) additional features. There's not much of value here, IMO, but free is cheap.