What kind of buttons? What actions are they performing? Are you sure your client is using Acrobat? (I have yet to see two copies of a PDF display differently, both in Acrobat except for a few minor bugs)? Do you have a sample you can post so we can test out your buttons ourselves?
The button is a graphic which is placed on the master page.
It's got the button feature added with go to destination - which then takes it to a page.
Sorry, I can't share the file as it's not my property.
What I might try is taking it out of the master page.
It's a mystery...
Is your client using Acrobat on a computer or on a mobile device? Acrobat for mobile doesn't support buttons.
What are your export settings?
Did you place the buttons on its own layer on top of the others, if they are on the master?
Yes, my client is viewing on an ipad - I am having to change everything to hyperlinks...
Your client is certainly not giving you accurate information. There is no Acrobat Pro for iPad so the client cannot be (like you) viewing in Pro... There is an Acrobat Reader but it cannot become the default reader. Good chance the user just opens in the default reader instead. You need to test your files on the target platform in the target viewer. If only the software makers had taken the P in PDF seriously.
The only problem with that is the number of devices and viewers out there. There may not be a target device.
Unfortunately, PDF, especially interactive PDF has become a victim of its own success.
Some interesting comments in there.
"Unfortunately, PDF, especially interactive PDF has become a victim of its own success."
I'd come to exactly the same conclusion.