How are you controlling the source property of the control, like Me.MyBrowserControlName.ControlSource = "=""C:\...\MyPdfName.pdf""" ?
I imagine it's an Adobe setting issue. Perhaps consider
https://www.accessforums.net/showthread.php?t=75727
or the solution here
https://stackoverflow.com/questions/...with-adobe-why
or do further research on "ms access pdf not opening in browser control" or similar. It seems to be a common issue and I get the sense that it's either due to Adobe settings or IE settings. If the problem pc's have one or the other Adobe product and they are having the problem, it would seem to point to Adobe settings as the culprit.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.