Read the topic just bellow you, called "Ultimate PDF to Epub/Mobi conversion tips". There's some good advice in there. Or do you just want a photo album (scans) disguised as an ePub?
PDF conversion has been beaten to death around here. You should search the forums.
- PDF is a bad format to convert, with the exception of tagged PDFs.
- Do not scan straight to PDF, always scan as images and work your way up (OCR, proofread, layout, etc, etc).