How to download a whole website as a single file (pdf). Please help me and thanks .
Try Offline Explorer, HTTrack or similar. You can print any webpage to PDF. I find pdfFactory Pro quite useful.
Try HTTrack. It wont work on Single Page Application. For the rest, it will leech all HTML and CSS, Javascript for you. It good for static sites, if the site is php or other language, you can reuse the html,css and javascript
check archivebox self-hosted web archive.
like Wayback Machine but self-hosted
You just made my day. Thank you 
!