Without a bit more information (such as platform - Windows or MacOS and version of same and version of InDesign), there isn't much we can do to even guess at the cause of your symptoms much less a solution.
PS: Acrobat doesn't “change files into .pdfs” but rather, can be part of the process of creating PDF files from other file formats.
We have windows 10, Acrobat 8, and Indesign CS3. And I understand, that was a poor choice of word (change vs create).
I was finally able to get hold of my son-in-law, and he was able to walk me through this issue. For some reason InDesign had reset itself to using Word. I'm the only one that uses this and I know I didn't reset it. Don't recall any updates lately.
Acrobat 8 is no longer supported by Adobe and most likely has not been updated to work with Windows 10. I would expect that some update to Widows 10 or InDesign broke the link to Acrobat 8. Even if you can reestablish the link you might lose in the future due to some update to Windows 10 or InDesign.