First, download and install iTunes.
Then, install it on your computer.
Step 1: Connect your iPhone to the computer and launch iTunes. Click on the three dots icon and select Books.
Step 2: From the File menu, choose Add File to Library, or use the shortcut Ctrl + O to add PDF files.
PDF is a highly secure format making it challenging to copy data from it. To copy data from a PDF, you need specialized software like Foxit Reader... There are various methods to copy data from PDFs that you can explore and follow the guides available on the Internet today.
Wishing you success! (Image source: Internet)