There are end of paragraph marks that need to be replaced with space characters. But if you just do that, you will lose the paragraph marks that you need, then ones that prevent the doc from being one long hunk of text. Those good paragraph marks are actually doubled, so to preserve them, replace every instance of two paragraph marks together with something that never occurs in the doc... like three z's together. Then replace the remaining paragraph marks with spaces. Then replace the zzz's with paragraph marks.

Here are the steps:

1. Make a copy of the document for a backup
2. Replace all 2 paragraph marks together with zzz
3. Replace all paragraph mark with a space
4. Replace all zzz with a paragraph mark