I've read the below answer : Font selection in XeTeX for specific characters
but I need a solution that works with pdflatex instead of xetex.
I've read the below answer : Font selection in XeTeX for specific characters
but I need a solution that works with pdflatex instead of xetex.
There is no correspondent in pdflatex of the “interchar tokens” feature of XeTeX. Making digits active for expanding them to add a font call is not a choice, as you want digits also for things like \linebreak[2] which would break painfully.
The only way out is to define a macro:
\newcommand{\printnum}[1]{{\fontfamily{...}\selectfont#1}}
where ... should be the family name of the font you want to use; then, to print a number with that font, say
\printnum{42}