If you don't mind using open source software, go to Sigil .
If you want to know the insides of how to create it manually, or some other tool, follow this. (This is a one-month course, so you won’t get all the content in one day).
- Create a folder structure. In the folder of your choice, create the following: META-INF (folder), OEBPS (folder), mimetype (file with the exact same name).
- Put application / epub + zip in the mimetype file. There are no lines without spaces.
- Convert PDF to text format. In Adobe acrobat, you will have the file> export>.
- Read the contents from the PDF, you will find some conclusions on how you can divide them into chapters or reading topics. Separate according to the understanding of the book and make so many text files.
- Create subfolder structure. Make Images , Text , Styles (folders) content.opf , toc.ncx (files) inside the OEBPS folder.
- Put all your split files in the Text folder created in step 5.
- put all the images extracted in pdf in the Pictures folder
- Place any styles (not described here) in the Styles folder.
- In the META-INF folder created in step 1, create a file called container.xml and fill in the following:
<?xml version="1.0"?><container version="1.0" xmlns="urn:oasis:names:tc:opendocument:xmlns:container"> <rootfiles> <rootfile full-path="OEBPS/content.opf" media-type="application/oebps-package+xml"/> </rootfiles></container> . - If you are able to do this a lot, sincerely, ping again, I will try to tell you what you should put in content.opf and toc.ncx in the one created in step 5.
As an example, you can use some examples from my site. Download from here and use them with caution. Do not distribute.