Your file is sent over an encrypted (HTTPS) connection to a conversion service, converted there, and sent straight back. It is not converted in your browser.
Mostly. Table grids, column alignment and paragraphs are rebuilt rather than dumped as plain text, though complex layouts may need a little touch-up.
Run it through OCR PDF first so the text can be recognized, then convert it.
Yes. Pick Excel (.xlsx), PowerPoint (.pptx) or CSV instead of Word (.docx) before you convert. The file is uploaded to the same conversion service either way.
No. Your Office file comes out clean, with no Utilitly branding.