Acctivate is a Windows application, but can be accessed from a variety of devices using a Remote Desktop connection.
There is not a native Mac OS or iOS app for Acctivate. However, the App Store offers Remote Desktop apps. You can install a Remote Desktop app on your device, then configure a connection to either your Desktop PC or a Terminal Server running Microsoft Windows. The windows in Acctivate work well on all tablets with a screen of 10" or larger.
Microsoft Windows App (previously Remote Desktop)
Microsoft has published their Windows App (Remote Desktop) for all platforms. This is the official Windows Remote Desktop app from Microsoft. It should be the most stable for accessing your Windows desktop or server computer. The Microsoft app offers a simple mechanism for pan/zoom and a button to toggle the keyboard. However, this app may require your IT/network support to set up a secure VPN or Remote Desktop gateway to access your work computer outside of your firewall.
You can download the Microsoft Windows App (Remote Desktop) in the Mac App Store, or App Store.
You can download the Microsoft Windows App (Remote Desktop) for Android tablets and devices in the Play Store.
There are other third-party apps from Parallels and other cloud providers. Please contact your IT or computer support team for more options.