Devonthink (document manager)
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Intended primarily for the paperless Mac office, this app saves all your documents, keeps them organized, and recalls them as needed. The publisher claims that there's no longer any need to store PDFs, bookmarks, and other info in separate apps.
It searches documents almost instantaneously, finds connections between them, extracts the most relevant topic words, and files documents automatically.
Some users claim that the interface is clumsy and unattractive. A direct competitor is Evernote (free).
There are four versions available on a free 30-day trial basis. A comparison chart is below.