The four platforms reviewed here — Sejda, PDF Buddy, Apple Preview, and Kdan PDF — span a range from minimal browser-based tools to multi-platform mobile-first suites. This page examines their capabilities in key areas relevant to individuals and small teams handling everyday document tasks.
It is worth noting upfront that these four tools are not direct competitors in every sense. Apple Preview is a system utility bundled with macOS, not a standalone commercial product. PDF Buddy is a narrow-scope web tool. Sejda and Kdan PDF are full commercial products with tiered pricing. Comparing them side by side is useful because users often consider all four when deciding whether a paid tool is necessary for their workflow.
All four platforms support annotation to varying degrees. Apple Preview and PDF Buddy focus on annotation as the primary editing mode — highlighting, freehand drawing, text boxes, and sticky notes. Sejda and Kdan PDF extend beyond markup into more substantive editing workflows while maintaining strong annotation capabilities.
Genuine text-layer editing — modifying the actual content of a PDF rather than placing text boxes over it — is a meaningful distinction. Sejda offers real text editing with moderate reflow capability. Kdan PDF provides basic text insertion. Apple Preview and PDF Buddy do not support text-layer editing; they overlay new elements rather than modifying existing content.
Electronic signature support is consistent across all four. Apple Preview's signature tool is tightly integrated with macOS and iOS — drawing directly or importing from the camera. Sejda, Kdan PDF, and PDF Buddy all support signature fields and basic form filling. Sejda additionally supports form creation, not just filling.
Platform availability is the most significant differentiator among these four. Apple Preview is macOS and iOS only — it does not exist on Windows, Android, or Linux. PDF Buddy is browser-only. Sejda supports Windows, macOS, and Linux both via browser and desktop app. Kdan PDF covers iOS, Android, Windows, and macOS with cloud synchronisation across devices.