Saving without affecting the file contents

Unfortunately, I could not add to this topic because it was closed. 

My question is: how can I save an existing pdf file in which I make some changes without affecting anything that is not changed? Let me explain. I have a pdf file, I reorder one page without making any other changes. How can I save the new file so that nothing else in the pdf is changed? If I first create a duplicate of the file in the OS file system, then reorder the page in Acrobat, then Save (ctrl+S), I still see a slight change in file size. Does that have any impact on the integrity of the file other than the order of that one change that changed?

Where can I see the metadata for the file? In particular is it possible to see any records of the changes made? I would like to compare the original pdf with the modified pdf (with the reordered page) saved with Save (ctrl+S)

Thanks.