Preview is the most underrated app on macOS. For viewing, basic annotation, sidebar reordering and quick signature stamps, it is free and excellent.
Flint covers what Preview cannot. Here is the boundary.
Where Preview wins
Free, fast, native. Drag-and-drop page reordering and merging in the sidebar. Decent annotation tools. Quick signature capture via trackpad or camera. For consumption and very light edits, it is enough.
Where Flint pulls ahead
Editing body text in place — Preview cannot. Real redact-pdf that removes content rather than covers it. Convert-pdf-to-word and back. Compress-pdf with control. Proper sign-pdf flow with saved signatures.
Best for…
Preview for view, comment and quick stamp signing. Flint as soon as you need to edit text, redact, convert or sign repeatedly.
How to combine them
Most Mac users keep Preview as default for double-click viewing and reach for Flint when they need real editing. That is the cheapest and cleanest setup.
FAQ
Can Preview merge PDFs?
Yes — drag a PDF into another's sidebar. It is the one place Preview shines for editing.
Can Preview edit text?
No. It annotates on top, not into.
Does Flint cost extra on Mac?
Flint is browser-based, so no different from any other platform.
Use Preview for free things, Flint for the rest.