Please specify the steps you’ve already taken (to solve the problem), so that we can rule out things.

I have some suggestions, but I do not know whether you already have tried these steps:

1) Selection Tool.

Select All.

Copy.

Create a fresh new document, and Paste all the music into the new document.

2) Export as a MusicXML file (File menu > Export > MusicXML…), then import the MusicXML file into a fresh, new document.

3) Use the Graphics Tool to export the document as a PDF file.

To avoid that the problem happens again, you could try some prophylactic steps (it could not hurt to try them):

Quit Finale.

Re-boot the computer.

Remove Finale’s Preferences file.

Launch Finale.

If nothing else, take screen shots of each page. You’ll have a starting point if all else fails.