The first page should be a landing page for a online tool to merge serveral PDF files to one. It should provide an smart userinterface to select various PDFs and upload them to the server. The design should be modern, very appealing and fast. A Google Pagespeed score of > 90 is required. Please do not use libraries like bootstrap which produce render blocking issues on mobile devices.
The second page should be a download page for the converted PDF. I should provide an optional progressbar. The converter in the backend does not need to be develped by you its about the design of the page.
Responsiveness and PageSpeed are key requirements! Also attractive design of course!