How Do I Convert a Pdf File To an EPub File?

I’ve been tasked with turning several works into ePub files. Most of the original files are documents that can be edited before publishing, but one of them is a pdf file (apparently the original document was lost). I tried copy and pasting from the pdf file into a Pages document, but the result was a formatting nightmare.
Is there a way to convert the pdf directly to an ePub and thus preserve the formatting? The export menu in Preview does not seem to have this option like Pages does.
I know there are online convertors (that may or may not work), but I’m not comfortable sending this person’s intellectual property through a 3rd party website.
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Cameron