I have had good results with Tesseract. I had to export the PDF to individual jpegs, then batch OCR'd them with tesseract, then merged the individual pages back into a single PDF. If you don't want to use command line and are okay with it not being open source, PDF24.org does a good job and does not charge.

Another vote for Tesseract -- just to clarify the terminology, though: PDF is a fragile format best used read-only; so you really don't want to edit a pdf, but make a new one using the same (or cleaned-up) bitmaps and a new ocr text layer.

Now, tesseract is excellent at recognizing glyphs; but especially if the scanned image is a little fuzzy, the layout detection falters; and when it falters, you get redundant line breaks, & chunks of text in the wrong order -- all of which gets incredibly annoying for searching & copying purposes. So if you can spare the time, and the text requires it, you may need to mark regions (paragraphs & titles mainly) on the bitmap image manually. There exist a few frontends to Tesseract that help with a task like that; check out, e.g., https://github.com/manisandro/gImageReader - inside single paragraph blocks of text, Tesseract doesn't get as easily confused; and the text output is in the correct reading order, & w/o redundant breaks.

Unfortunately, that's kind of the state of things. From what I know, editing PDFs requires expensive licensing from Adobe and that's why you have to pay for most editors.

Have you tried recreating the faulty page, then printing as PDF and splicing it in with a free web PDF recombiner like ilovepdf?