Google is your friend. Noting that EPUB is basically HTML:
https://pdfbox.apache.org/
https://www.idrsolutions.com/pdf-to-html5-svg-converter
http://cssbox.sourceforge.net/pdf2dom/
amongst others.
To second pdurrant: PDF to anything is a *very hard problem*. Unless your use case is trivial, it is hard to imagine producing acceptable-quality output.