PDFinternals

PDF internals is a free app that let's you see inside your PDF files and get at the internal details that are normally hidden from view.

It is a companion to "PDFcompare", a ( not free ) app that lets you compare all this data as well as the visual page images to do a diff between two PDFs. Available here: https://www.microsoft.com/en-us/store/p/pdfcompare/9n9dmzjbz2nl

The PDF format is a very complex format and contains a lot more information beyond that which a normal PDF reader shows you.
PDF internals shows you the normal view that you see in your PDF reader but it goes much further and lets you examine the hidden meta-information, the internal page structure, and what is inside each and every object that makes up your pdf file.

This is also useful in a business environment to let you examine what changes have been made to a file, when and by whom; or check what hidden information you or others may be leaking out.

See what's really inside your PDFs - get PDFinternals.

And try PDFcompare to compare two PDFs: https://www.microsoft.com/en-us/store/p/pdfcompare/9n9dmzjbz2nl