Adobe Acrobat Pro DC 2022.001.20117: How to identify the resolution (in dpi) of a scanned pdf file?

PDF files don't have a resolution, as each image in them could have a different resolution value.

Since you have Acrobat Pro you can export the images from the PDF and then examine them directly, or use the Preflight tool to check what they are.

With the preflight tool of Adobe Acrobat Pro you can check the resolution of the images.