Begin by logging in to this site on your iPad and tap on the PDF download link.
Step 1. Tap the icon in the top right corner as shown
Step 2. That opens up the menu and then select Copy to Books
Step 3. This imports the PDF into Books and from then on, you can access it by opening Books.
Step 4. Once in Books, if you touch Collections, you can select PDFs and then select your manual.