RSSme - RSSme is free, lightweight and user-friendly RSS editor.
MarsEdit - MarsEdit is a desktop blog editing application for the Mac. It provides an offline interface to most popular blogging systems. WordPress, Blogger, Tumblr, Movable Type, and many other systems are supported.
Feed Launch .NET - Feed Launch .NET is an open-source feed editor for RSS 2.0 and ATOM 1.0 Feeds.
PDF Professional - PDF Professional is a feature-rich PDF Ultimate Solution for reading, annotating, form filling, editing, signing, and converting PDFs on your Mac, iPhone and iPad.
Feeder by Reinvented Software - Feeder is for creating, editing and publishing RSS feeds on macOS.
Marvin Classic - Marvin Classic is free to use the web and mobile application specially designed for ebook lovers who want to read, manage, and download new ebooks.