After a few failed attempts, and with lightening speed of pressing the suggested keys, I was able to see the "Delete Preference" message, but it didn't solve the real problem, that the 100 plus layers of documents were not showing in the layer panel, which I could select and merge them to flatten the document for the printer. Someone told that the preferences are not related to the Layers visibility issue. Reinstalling CC Suite also didn't work. A friend suggested that I didn't need to flatten the document, because it gets flattened when you export it in PDF Print file. By the way my printer wants Compression box unchecked. I hope this is correct and it works. I am sending the document to the printer in a day or two. Thanks for your input.
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