[CentOS] Substitute pdftk with other command

Hi, I must migrate a Centos5 server on Centos7

On server Centos5 there is a shell procedure witch add to PDF a
timestamp like this example:

http://i.stack.imgur.com/OBsqX.png

with this command:
$ pdftk input.pdf stamp overlay.pdf output stamped.pdf

Into Centos7 pdftk it is no longer allowed

Someone knows some other command to replace it or other ways to do
this?

Or how I can install pdftk on Centos7.

Many thanks for your help.


--
Dario Lesca
(inviato dal mio Linux Fedora 23 Workstation)