How can I type 'Assamese language, India' in Adobe PageMaker 7 in Windows 8.1 Pro x64 environment ?
You will run into many problems as pagemaker is obsolete. It really only runs under win xp. Some people claim they can get it to run on windows 7, 8 but often run into problems when it comes to printing/pdf creation.
The other problem is that pagemaker will only support the first 255 characters in a font, which severely limits it's usefulness. There was a middle eastern version of pagemaker with special fonts, but I don't think it's still available.
I would look into Indesign, but research the language support before commiting to Indesign, as it may require some additional software, and or workarounds. Post your question in the Indesign forums.
Exactly what Jay said...