I know that not too long ago I was running a program to edit pdf files, but I am pretty sure that was a linux thing so perhaps not everyone could do it. I edit pdf files too, but they are text. These are image files and not text. If I changed them, the metadata would indicate that.
Hmmm. When I save a converted file to a pdf, the metadata shows it as being unchanged. Since it was created with a combination of text and pics and then saved as a pdf, as far as the metadata is concerned it is an original file and unchanged from its creation date.
But OK. I understand your preferences and thanks for the clarification. :)