PDF to EPUB doable?

Calibre will work for this, but it almost certainly won't give a good result. That's not Calibre's fault; Adobe InDesign produces exactly the same horrible output from a PDF. It's just a reality that PDF does not lend itself gracefully to being converted easily to a well behaved EPUB.

Unless you are converting something extremely simple with no inline images or interesting text layout, getting a nice EPUB will almost definitely be a tedious process of fiddling directly with the HTML and CSS with something like Sigil (or Calibre, but it's not as nice).

If the reason for this is reading a large PDF on a small screen, I suggest enabling Reflow in Koreader

k2pdfopt that I used ages ago works similarly but with Koreader I can just open the files without having to prepare them first

Depends on the PDF... It's a container format - so it depends on what it contains.

So the easy answer to your simple question is, that yes, it's doable - sometimes, and sometimes it is not.

I've done it with Calibre.

Results vary, but if it's a simple enough document without too many images or formatting, it should come out very readable.

I've been using this site to convert to PDF for forever, so I'm assuming it'll also be good for the other way around

https://ebook.online-convert.com/convert-to-epub

Calibre does not do the job

To anyone hassling in the future with this: Open pdf with Abby Reader OCR-->Export to Epub-->Use Calibre to convert Epub to Mobi

There's something tricky about converting pdf to epub that I can never get to work properly. Maybe it's too do with the way the pdf is put together?

I could highlight the text of the pdf and paste it into a document but it would come out different in places. I tried this experiment because the calibre conversion was doing the same thing.

I tried many online converters but none of them could do it either. In the end, I read the converted epub and just had to mentally correct the words that didn't properly convert.