If you can use either XeLaTeX or LuaLaTeX instead of PDFLaTeX, you could enter Devanagari in Unicode, with either babel or polyglossia.
Otherwise, if you just need to insert a single short passage, you could compile it to a stand-alone PDF and include that.
If you first compile this file in XeLaTeX or a version of LuaLaTeX that supports HarfBuzz:
%% This document requires LuaLaTeX 1.12.0 or higher, or XeLaTeX.
\tracinglostchars=2 % Warn if the current font lacks a character.
\documentclass{standalone}
\usepackage{polyglossia}
\ifLuaTeX
\defaultfontfeatures{ Scale=MatchUppercase, Renderer=HarfBuzz }
\else
\defaultfontfeatures{Scale=MatchUppercase}
\fi
\setdefaultlanguage{sanskrit}
\newfontfamily\sanskritfont{Shobhika}[
Script = Devanagari,
Language = Sanskrit]
\begin{document}
वसुधैव कुटुम्बकम्
\end{document}
You get the following PDF as output:

Save this as vasudhaiva.pdf, and you can now make a new PDF that complies with PDFLaTeX:
\documentclass{article}
\usepackage[paperwidth=10cm,
paperheight=3cm]{geometry} % Solely to format the MWE for TeX.SX.
\usepackage{cmap} % For copying from PDF.
\usepackage{graphicx} % For \includegraphics
\usepackage{lmodern} % Or your font of choice.
\newlength{\Hheight}
\newcommand\vasudhaiva{%
\settoheight{\Hheight}{H}% Not quite enough, because of ascenders.
\includegraphics[height=1.25\Hheight]{vasudhaiva.pdf}}
\begin{document}
\textit{Vasudhaiva Kutumbakam}
(\vasudhaiva)
is Sanskrit for, “The World is one family.”\footnote{Footnote size: \vasudhaiva.}
\end{document}

You can use any OpenType font that supports Devanagari, it will be scalable, and you can even copy and paste the text from the PDF.
Since this is a single image, you do not get any line breaking. If you’re willing to put up with more of a headache to be able to word-wrap, you could create PDF files for each individual word and include each of them, separated by \ . If you do this, you might want to throw in a \vphantom{सुधै} to ensure that the PDF files have the same height and depth.