The tools on this website run in your browser. The PDF, the Word file, or the spreadsheet is read by code on the page. SKY13.app does not offer an upload box for those tools and does not store the documents. When you download a result, that file is created on your device.
On a first visit the interface follows where the site is opened: Hindi in India, English elsewhere. A browser set to Hindi still opens in Hindi. After you pick a language, that choice is remembered on this device. Currency stays separate, so Hindi can still show prices in dollars, euros, or rupees.
OCR is the exception that uses the network, and only for the recognition engine. The first time you recognize text, the browser may download language data. That is not an upload of the PDF. If you are offline, OCR will not start, and the other tools still work.
This version does not password-protect a file, unlock one, or rebuild a complex PowerPoint or a designed Word layout. Those jobs are easy to fake and hard to do truthfully in a page. The pages say what they actually change. Advertising, if you accept it, is labeled and kept away from the file buttons.