I offer e-book formatting services to create Kindle (MOBI), EPUB, and PDF electronic books and documents. The books are generally formatted to the Smashwords style guide, allowing you to publish your book through Smashwords or similar services.
The most common formats from which e-books are created are Word, RTF, and HTML documents.
The cover art for the e-book should typically be at least 2500 pixels on the long dimension. No back cover art is needed for an e-book. The cover art may need to be resized down somewhat for some formats in order to accommodate the limits of various e-readers.
If you will publish your e-book with an ISBN, you will need a separate ISBN for each distinct format (Kindle, EPUB, PDF, etc.).
I have successfully created e-books by extracting the text from an original PDF file. These documents require additional work to create an RTF file from the extracted text, from which the e-book can then be created. The amount of work required depends on the details of the text, such as footnotes and block quotes. This is because text extracted from a PDF is not structured in chapters, and all non-standard paragraph formatting, such as margin indented block quotes, are lost and must be recreated. If the document contains footnotes or endnotes, these must be manually recreated by deleting the foonote text and footnote reference, then creating a new footnote; this is necessary for each footnote.
A few remarks on e-books may be helpful to understand what you will receive. The Table of Contents is automatically created and inserted at the beginning of the e-book. Footnotes are automatically converted to endnotes and placed at the very end of the document. Though this is not where endnotes are placed in a paper book, since the footnote references are dynamically linked, their placement at the end of the document does not really matter because they are referenced differently.
There are differences in how the Kindle and EPUB formats are read. The Kindle format and readers are tightly controlled by Amazon, and what the reader sees generally closely follows the published format. In contrast, there are many EPUB readers, and many of them by default reformat the text to what they consider optimal. This characteristic of EPUB readers can be annoying, as special features such as full block paragraphs and block quote indenting, which may be necessary to visually structure the text to be easily readable, can be lost. Generally the best option is to request your readers to set their EPUB readers to use the publisher defaults.
Feel free to contact me; I would be happy to discuss your particular e-book project with you.