On certain Adobe documents I receive, when I start to scroll down the page a box pops up that says "Illegal characters in name". I close the box, and as soon as I start scrolling, the box pops up again.
That's very likely a sign of a corrupt PDF. The "name" is actually a part of the PDF structure. If this is a PDF file you've created, re-create it and see if you still get the problem. If it's from some other source, complain to the author or distributor and see if you can get a clean version of the document.
Thank you. It is from an engineering company returning marked up submittals from my company. The only page that is corrupt is the cover sheet they added. I will complain to them!
It's very likely caused by the software they are using to create that cover sheet.