The Devnag font will need to be installed on your own particular computer device.
When displaying the content, the problem font will be embedded in the pdf file, along with its built- in hypertext tags to tell the pdf reader to switch language fonts.
To search the content for Devanagari - you have to write in Devanagari - if your system is able to....
First you could try and copy a string of Devnag from the text and paste that into the search box.
If you see garbage characters, you have some work to do....
Fonts?
The reader will tell you:
For Foxit Reader for example I access the its main menu:
File, then Properties, then Fonts.
(Adobe is much the same)
Voila! all the required fonts are listed.
It's up to you to find those fonts on the internet, download and install them.
Then, I assume you have a utility to switch keyboard language,
you must switch to a suitable font on your device before you can type away.
That's it!
Tecnical point, if you use a slow mobile or such.
Embedded fonts contain only the characters that it actually uses, to reduce file size.
Downloaded fonts may be bi-, tri- multi- lingual... and much bigger.
Taff_Rivers