When converting from PDF to e-book formats CloudConvert (
https://cloudconvert.com) will remove line end hard returns and maintain paragraph integrity. This was after trying all the line length adjustments in Calibre conversion which increasingly failed to work. I prefer to convert to DOCX so that I can easily create a ToC before converting to EPUB or MOBI formats for my Kindle. I know that Calibre developers are working on a new PDF conversion tool and wonder whether CloudConvert is using an opensource code or developing its proprietary product in-house for commercial purposes. CloudConvert is effectively a free online tool since restrictions on daily volume is very generous.