Prakashsingh04/PDF-DOST ? reverse-engineered prompt

Build me a modern web app called PDF DOST where someone can upload a PDF, see it previewed right inside the page, and ask questions about it in plain English.

I want a clean split screen layout with the chat on one side and the PDF viewer on the other, plus an easy way to hide the preview if I just want to focus on the conversation. Make the upload flow simple, with drag and drop support, and show the file name once a PDF is loaded. The chat should feel fast and friendly, with clear message bubbles and helpful answers that can summarize sections, explain parts of the document, and answer specific questions from the PDF.

Please make it look polished and responsive, with a dark modern style. If you need to look up current docs for the PDF viewer or UI pieces, go ahead and do that.