Yes, as long as the e-book is DRM-free (or you know how to crack the DRM). As the other person mentioned, applications like Calibre will do it for you automatically. Of course, the PDF will probably not look as good as a custom-crafted PDF, because e-book formats and PDF formats are meant for different uses, and most publishers manually tweak their PDFs to look their best in ways that aren't possible with automatic conversions. But if you're just wanting to be able to print out a copy of that e-book, or read it on a device that can only do PDFs, Calibre will do the job for you.
And, of course, Adobe Reader is more than capable of converting text to any other format that you can name. If you do need to convert to a PDF and make your manuscript look more professional, that's another option. A more specific question: The e-book formatting requirements in your publisher's style guide? For example, is there such thing as PUB and/or MOB? What are their pros and cons? I can't really comment on this, since not too much I know about those formats is public. The format in PDF that is likely to be the most popular among all of meek-and-dim readers is PUB. MOB is the format most likely to be preferred by professional publishing houses. It has its own set of pros and cons. So, to answer your first question, in most cases both PUB and MOB are more or less equivalent. And if you're just looking.