When you edit a GPO, using the Group Policy Object Editor snap-in, the ADM files are loaded from the Group Policy Template in the domain controller's Sysvol folder. This allows you to use the same version of the ADM files that were used to create the GPO while editing the GPO.
If you wanted to localize the ADM file to see the text in a specific language, you can implement the Always use local ADM files for Group Policy Object Editor policy on a computer that uses the specific language, causing the Group Policy Object Editor to load the files from that computers %SystemRoot%\inf folder.
The Always use local ADM files for Group Policy Object Editor policy is configured at Computer Configuration / Administrative Templates / System / Group Policy.
NOTE: Enabling the Always use local ADM files for Group Policy Object Editor policy sets the OnlyUseLocalAdminFiles Value Name,
a REG_DWORD data type, at HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\Group Policy to 1.
NOTE: You must use a computer that has the ADM files that your require in the %SystemRoot%\inf folder.