All this, of course, presupposes that you have the software and the skills to create the book on your computer. If you don't you will need to get it done professionally by a local agency like BriarsBooks. That person will create the book and PDF and EPUB for you.
IF you have created your book in MSWord, Word will allow you to easily save your book file as a PDF. PDFs will exactly mirror your book layout but will be fixed, not reflowable. Creating an EPUB from your book is trickier. The Daisy Consortium provides a free Word to EPUB addin that will convert your word document to EPUB BUT your Word document MUST be correctly formatted using style sheets etc for this to work. There are also online conversion tools though the result may require formatting changes in an EPUB editor.
BUT if you're wanting people to BUY the PDF and/or EPUB book from your website then you're best to put the files behind a shopwall, ie., create a shop store on your website. Shopify is easily the most popular way of doing this. It can be integrated directly into an existing website regardless of the platform it is built on. You will need to set up a Shopify account. Processing is secure and hosting reliable. The starter plan will probably be all you need and it's not expensive. If you don't have a shop you will just have to be philanthropic and let people download free of charge.
If playing around with Shopify, PDFs and EPUBs of your book is not something you want to do, then you're best to bite the bullet and create a ebook on Amazon KDP and let the digital bookstore promote and sell it for you. Or get someone else to create the book for you.