Thank you Bruce, I will check the link.
There were times when I downloaded PDFs from other sites and got the purple note, but not when I've made my own file.
I have Acrobat Reader DC and Adobe Acrobat 9 Pro. Also, I'm still on Windows 8.
Meanwhile, one of my testers sent me this info:
I use windows 10, Microsoft edge and the latest adobe reader 32. Still no calcs.