Qiqqa is by far the strongest solution for research and managing pdf's. Zotero, named as a comparison is weak as it does not allow pdf;s to be loaded into its interface - you need to use a pdf reader, which defeats its whole purpose. With Qiqqa documents in a library can be searched together. It has excellent maps of your libraries. It is not prefect, having a few glitches, but still is the only one of its kind.
Based on our record, Leap seems to be more popular. It has been mentiond 3 times since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
+1 on the need for non-Spotlight options. Source code makes a mess of spotlight for everyday usage. I like Leap a lot for multimedia browsing with more precise search capabilities than spotlight: https://ironicsoftware.com/leap/. - Source: Hacker News / 5 months ago
Just use tags for everything and don’t worry that much about the file hierarchy. This will let you take advantage of automatic downloading systems like the apps that DriveThruRPG and itch provide. Point Leap at your collection and use it to find stuff. Source: over 1 year ago
You might also look into Leap for tracking/tagging stuff. Source: over 1 year ago
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
Elyse - The free version allows up to 30 tags.
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
HoudahSpot - Advanced File Search Utility for Mac OS X
JabRef - Graphical Java application for managing bibtex (. bib) databases.JabRef · JabRef Help · JabRef | Blog · OpenOffice/LibreOffice .
TaggedFrog - Based on the convenient drag ’n’ drop technique, TaggedFrog allows you to organize your files...