As per Rule 11 Sub rule (8) of Central excise Rules, 2015 and Notification number 5/2015-service tax dated 01.03.2015 rule 4c Any invoice,bill or challan issued under rule 4A or consignment note issued under rule 4B may be authenticated by means of a Digital Signature with effect from 1st March, 2015. Read More>>

Save Trees! Use Digital Signatures

"Apart from Invoice the same can be used to Digitally sign any PDF documents and also encrypt the same"