MOBI sang PDF

Only if they're DRM-free. Most Kindle store purchases carry DRM and the tool can't open them. Personal documents, public domain books, and titles from DRM-free stores convert normally.

No. Only files with the .mobi extension are accepted. Convert other Kindle formats to MOBI or EPUB with another program first; EPUB files can then go through EPUB to PDF.

No. MOBI text reflows to fit whatever screen it's on, so the engine lays it out onto fixed-size pages of its own. PDF page numbers won't line up with Kindle locations, and there's no setting for page size or font size.

Headings, bold and italic text, lists, and embedded images carry over. The text stays real text rather than an image, so it's selectable and searchable in the PDF.

Yes. One file downloads as a PDF named after the book; several files are converted one after another and delivered as mobi-converted.zip with one PDF each.

The usual cause is DRM. Corrupted downloads and files that were renamed to .mobi without actually being MOBI files also fail. If the same book opens in Calibre, converting it there to a fresh MOBI usually produces a file this tool can handle.

No. The conversion engine (PyMuPDF compiled to WebAssembly) is downloaded from a CDN the first time you use it and then runs inside your browser, so the book itself never leaves your device.