The conversion to PDF is supposed to be a one-way process. In other words, once you've made a PDF, you don't edit it. That's the point. If it needs to be edited, you edit the original document then make a new PDF. PDF conversion tools convert TO PDF, not FROM PDF.
Anyway, to answer your question, the easiest way to edit PDF info is to highlight the document's content, copy, and paste into an editable document. I doubt this will pick up images, and this will not work with copy-protected PDFs. If that's what you want you're pretty much out of luck.