How to add digital signature into RTF I-expense report

Dears,

After I-Expense report approval, the end user print the I-expense as PDF file and sign it manually and give it to finance team to be reimbursed

as end users working in different location them finance team, I have one request :

by printing the I-expense report the digital signature for the specific employee should comes into the print out

how can I proceed for that?

Note:

report output :RTF (using XML publisher)

EBS suite R12.1.3

DB: 12

OS: Windows 2008 R2 server

Regards

Chaker