This article explains the procedure on how to upgrade Policy Enforcer

To upgrade your Policy Enforcer software to the latest release:

1. Access the Policy Enforcer software download page

https://www.juniper.net/support/downloads/?p=sdpe

2. From the Version drop-down menu, select the version you want to install.

3. From under the Application Package heading, download the Policy Enforcer RPM to your Policy Enforcer virtual appliance.

4. On your Policy Enforcer virtual appliance, change directory to where you downloaded the RPM bundle and install it using the following command:

[root@hostname~]# rpm -Uvh filename.rpm

Sample 

[root@pe tmp]# rpm -Uvh Policy_Enforcer-23.1R1-1393-PE-Upgrade.rpm 
Preparing...                          ################################# [100%]
Updating / installing...
   1:Policy_Enforcer-23.1R1-1393      ################################# [100%]
Upgrading..
Upgrading from  22.3R1-1382 to 23.1R1. It may take up to 5 minutes.
Logging to /var/log/pe_upgrade_23_1_1.log.
Please wait for the upgrade to complete. Do not end the execution.
Upgrade successful
Done.

[root@pe tmp]# cat /etc/redhat-release 
CentOS Linux release 7.9.2009 (Core)
Policy Enforcer Package Version: 23.1R1

Note: It may take a few minutes to install the RPM bundle. Once installed, the Policy Enforcer screens within Security Director and any schema changes are updated. The configuration settings you used when you deployed the Policy Enforcer VM are retained

5. To verify: In Security Director, select Administration > PE settings. This page shows the current installed Policy Enforcer version number.