Elsi, as Dale points out there are many possible methods to accomplish the goal of getting from a pbook/image file to a finished file ready for conversion to an ebook.
I just looked at the Wiki thread on
Digitizing Paper Books to Ebooks and it is a good start. I will augment it with some of the techniques and tools that I have used.
Some books scan so cleanly that there is very little touch-up required after the OCR conversion. Others are in such bad shape that it is easier to retype the book than it is to clean up the OCRed text. With very few exceptions the books I have converted this way used the basic US English language and character set -- no accented characters or extra "u"s in "color" for example.
It is a long weekend, I'll see what I can get finished then.