So, you scanned something in, but it could use some editing before you commit it to a PDF or try to do OCR (Optical Character Recognition) to convert it to text.
One free solution is Scan Tailor. “Scan Tailor is an interactive post-processing tool for scanned pages. It performs operations such as page splitting, deskewing, adding/removing borders, and others. You give it raw scans, and you get pages ready to be printed or assembled into a PDF or DJVU file. Scanning, optical character recognition, and assembling multi-page documents are out of scope of this project.”