Every tool, no login screen
Merge, split, compress, sign, lock, unlock — the full PrivaPDF toolkit works without logging in, on the free tier's daily usage allowance. A login only becomes relevant if you want to remove the daily cap on the Pro plan, not to use the tools at all.
That matters on shared or work computers where creating yet another account isn't something you want to do just to fix one PDF, or where IT policy discourages signing into third-party services from a work machine.