Display Currency Code Or Symbol in invoice pdf without changing core files

1.Download font that support Any Symbol Like  Indian Rupee symbol. recommended dejavu-sans font.
http://dejavu-fonts.org/wiki/Download
https://sourceforge.net/projects/dejavu/files/dejavu/2.36/dejavu-sans-ttf-2.36.zip/download

2.Place the font in lib directory(Magento Directory/lib).

3.open app/code/core/Mage/Sales/Model/Order/Pdf/Abstract.php and app/code/core/Mage/Sales/Model/Order/Pdf/Items/Abstract.php

copy paste both files under local

1.  app/code/local/Mage/Sales/Model/Order/Pdf/Abstract.php
2. app/code/local/Mage/Sales/Model/Order/Pdf/Items/Abstract.php

and replace

$font = Zend_Pdf_Font::fontWithPath(Mage::getBaseDir() . '/lib/LinLibertineFont/LinLibertine_Re-4.4.1.ttf');

with

$font = Zend_Pdf_Font::fontWithPath(Mage::getBaseDir() . '/lib/dejavu-sans/DejaVuSans.ttf');

(in _setFontRegular(), _setFontBold(), _setFontItalic() functions in both files.)

Admin -> System --> Manage Currency -->Symbols --> Copy your symbol and save.