Make Adobe the default reader Win 8.1

Here's my issue. I am Tech for our School District. We have a whole passel of student computers that utilize a testing program that allows the students to printout their test reports. The test reports are in PDF format. Not a problem. For some reason they will not print unless Adobe is the default program for .pdfs. That's a problem. I have uninstalled the MS reader and made Adobe the default, and that works great for that particular user/profile. MS reader remains the default reader for everyone else.

Is there anyway to make Adobe the default reader for all the users? I am sure it's something so simple and I am just having a loss of gray matter.

Thanks...

looks possible via GPO (assuming you're on a domain):

https://technet.microsoft.com/en-us/library/cc754587.aspx?f=255&MSPPError=-2147217396

We are on a Domain, I was wondering if something could be through GPO. I'll see what I can do, Thanks.