I have been trying to use Helvetica font while creating the pdf but the font is not reflected back in pdf.
I did some google and found some solutions but none are wo
For me loading fonts from Google Fonts didn't work. And putting base64ed binary into a CSS file seems a little to much for me(Korean types are several megabytes). I'd recommend to install the fonts you need to use on the machine. For Ubuntu you can simply download fonts files from Google Fonts and copy the files in to $HOME/.fonts directory and run fc-cache command in command line to rebuild the fonts list.
$ mkdir ~/.fonts
$ copy your-font-file.ttf ~/.fonts/
$ fc-cache -fv
For a Rails application you can symlink
$ ln -s /your/app/root/assets/fonts ~/.fonts
Then you will be able to list all available fonts.
$ fc-list
Nimbus Sans L:style=Regular Italic
URW Palladio L:style=Roman
Century Schoolbook L:style=Bold Italic
Nimbus Sans L:style=Bold
URW Chancery L:style=Medium Italic
Nimbus Roman No9 L:style=Regular
Century Schoolbook L:style=Bold
Century Schoolbook L:style=Italic
Nimbus Sans L:style=Regular
....