A tool I find so necessary in editing/creating epub is editpad. I prefer the EditPad Pro because of the additional features such as being able to add a spell checker but EditPad Lite is equally useful. I actually use both programs.
I can open multiple files at the same time so find it very useful in conversion of multiple pdf files after converting them to basic html.
Many pdf's convert with the same problems.
Problems such as <br/> or <br> instead of <p> tags or use of only the opening tag or outdated html such as <center> or <big> can then be searched across multiple files.
The ability to use regular expressions to find the <br> tag that is followed by a lowercase letter and replace it with a space across say five or ten files at a time is something that saves so much time.
Another feature is being able to find the next and replace or skip as you choose with just a click saves time also.
I find that editing multiple files with similar problems cuts the "cleanup" time significantly. This may be in part because you can then use the same css stylesheets and streamline the editing process.