Description of App
calibre is a free and open source e-book library management application developed by users of e-books for users of e-books. It has a cornucopia of features divided into the following main categories: Library management, ebook conversion, syncing to ebook reader devices, downloading news from the web and converting it into ebook form, comprehensive ebook viewer and content server for online access to your ebook collection.
How to easily convert books, documents, e.g. PDF to HTML or EPUB
if you want better navigation, reading, or text selection capabilities than those currently available for PDFs on Mac, but don't mind loosing PDF features such as notes and highlights, then converting PDF to a format such as HTML, EPUB, DOCX, RTF or plain text might be the way to go. Calibre for Mac can convert to all of these formats and between many more others, no command line needed, although it requires few tricks to deal with its bad accessibility, like switching to newly opened pop-up windows using VO + F2 + F2, or activating pop-up menu items with a mouse click using VO + Shift + Space bar.
To select a book you previously added, for instance by pressing the "A" key, and to convert it to another format, you have to move the keyboard focus to the list of books in the main window, specifically, to the item which says "empty, table", VO + Command + T sometimes lets you to focus it, and then you can use Up and Down arrow to move between your books in the table even though VoiceOver won't announce anything as you actually navigate the table. However, you can press the "I" or "E" key to display information about the currently selected book, then close it, and press the "C" key to open the book conversion window for the currently selected books, where you have to utilize the aforementioned tricks to choose the output format, for instance. Knowing this, converting a book or document is a fairly quick process, and you might be able to convert multiple documents if you manage to select those you want using Shift + Up or Down arrow, or Command + A, in the books table, possibly filtering the table using the search field, Command + F.
Therefore, as far as editing books metadata or conversion is needed, Calibre is usable, but with other features, such as book reading or tags editing, I have experienced inaccessibility or freezing.