Where can you find a legitimate, verified digital copy? Below are the only three authoritative sources that meet academic standards.
KITLV (Royal Netherlands Institute of Southeast Asian and Caribbean Studies) : Many studies of the text are published here. kitab negarakertagama pdf verified
The most useful verified PDF for non-experts is the English translation and transliteration by (1995, KITLV Press). Where can you find a legitimate, verified digital copy