No per-file or per-merge limits
Some free merge tools cap you at 2-3 files or watermark the output past a certain file count, nudging you toward a paid tier. PrivaPDF's merge tool has no server-imposed limit on how many PDFs you combine — the practical ceiling is just how much your device's memory can hold, since everything happens locally.
Drag files in, reorder them by dragging thumbnails, and merge — the whole process stays inside the browser tab, so combining ten scanned receipts or three chapters of a report costs nothing and uploads nothing.