Cant Copy paste Hindi in other Fonts

I need to make a poster with stylized hindi fonts in it's headings. I have enabled world ready layout with middle eastern features and missing glyph protection. I have tried copying the hindi text from excel, word and RTF files but they get pasted in the Adobe Devnagri Font everytime. When I select the text and change it to the font SHREE DEV7 2453 or any other font i downloaded from the web, it just turns to Boxes (image attached). I converted it to unicode, the same thing happened. Even tried from unicode to kruti dev, still the same. I can type in the custom font when it is selected but I dont know how to type in hindi so i have to copy paste and whenever I do so, it turns into boxes. I have tried the google Input tools as well but it still doesnt work and turns into boxes whenever I input the words i want to type. I've tried all  this on multiple PCs. I'd really appreciate the help, been banging my head at this for hours. Thanks in advance.