Originally Posted by Elfuente
could you give a quick step by step guide how you do that. I didnīt find out how convert the .html either to pdf, .mobi or epub
In MobiPocket creator import the PDF. The software will then do its thing and dump the resultant .html file and associated images in a folder in your home directory somewhere, and offer to display the files. It will also offer to create a .mobi, which you can skip since everything Calibre needs is there already. Then import the .html into Calibre, which will show up as a .zip (including the images), and convert that to .ePub.
Attached is a screenshot showing the original PDF, the files MobiPocket creator created, and the end-product .ePub after importing and converting with Calibre (I imported the files over to MacOS as MobiPocket unfortunately is Windows-only, so this is even easier in Windows). The original PDF is unreadable with tiny text, while converting directly with Calibre results in a mess of layout artefacts, but using MobiPocket as the front-end results in a final .ePub that looks like an official ePub, for a book that's very unlikely to ever get an ebook release. Would be amazing if Calibre could do this itself, but it's really focused on transcoding between well-formed XML formats, not intelligently dealing with layout issued from a PDF.
I've also had good success with MobiPocket with multi-column documents, and even some docs I scanned and OCR'd myself using Acrobat. Calibre doesn't even come close.
p.s. tried to convert the same book from PDF to .html with Acrobat to see how they stack up: the Acrobat conversion was totally unreadable: inserted random spaces inside words everywhere for reasons I can't figure out since they're not in the raw text if I just copy-paste it. The only thing Acrobat seems to have over MobiPocket is better handling of tables. Also the notable downside of costing money.