Calibre forum. And
link to Calibre homepage, where you can download it free.
Unfortunately, there's nothing that converts all PDFs to easy-to-use ebook formats; how well the conversion works depends on how the PDF was initially made, and you don't get any control over that. Some PDFs will convert cleanly; some will convert with headers as text and a hard return after every line. It's why ebook advocates generally hate PDFs; while they *can* be good ebooks, they have to be made right for that to be true, and most of them aren't; they're made for printing.