How to embed Khmer Unicode Font

I am Cambodia, I speak Khmer. There are also Khmer fonts in Google Font, but I don’t know how to link them to my post written in Khmer. So I just Alt+Shift, then type in unicode provided with Windows 7. They enter just fine, but some characters will be missed if browsed by computer without proper Khmer unicode.

One of the example: https://soweic.com/2011/using-dropbox-storage/
You will see the different between .pdf file and one written in the post if you have no Khmer unicode.

Thanks in advance for your answers.