If you’ve consistently used the same font throughout, then see this thread for a solution. (If I weren’t typing this on my phone, I would have copied over the key points. 
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That thread has a link to a knowledge base article that explains how to set your default formatting for new documents and then how to apply that to existing documents.
If you have different fonts sprinkled throughout your project, then that method probably isn’t the way to go, as it will reset your fonts too.
You may want to first try it on a copy of your project to make sure you’re happy with the results.
Best,
Jim