Layout's Default Logo showing up on emailed PDF

I accessed a large Dropbox file I sent to a client and discovered Layout’s default ‘cover page’ superimposed over every sheet (8-1/2x11). My PDF files (derived from a Layout file) on my PC do not show such superimposition. My Layout file prior to exporting to PDF and post exporting do not show the superimposition. They looked good so I sent them, only to later discover this embarrassing addition that looks like a grave error. Any ideas what happened? I now recall a contractor had a similar problem. Meeting on the jobsite with him once I saw the same problem on his drawings, drawings I had emailed him in PDF form. Greatly appreciate any insight.