Since you're goi to update your iPad, it might be better if you did a reset to its factory default condition, using iTunes, to get a clean installation, since many people have been reporting problems with a standard upgrade procedure.
ALSO ... be sure to do your backups first and understand what will not be included in your backup. Use the iTunes program for your backup if you can. When you do the factory reset, be sure your computer has the anti-virus program turned off for the procedure with the iPad.
Here are some links for you ...
Choosing an iOS Backup Method (Should I Use iTunes or iCloud to back up ...)
https://support.apple.com/kb/HT5262
Back up and Restore your iOS Device with iCloud or iTunes
http://support.apple.com/kb/ht1766
iTunes: About iOS Backups
http://support.apple.com/kb/ht4946
Create and Delete iPhone, iPad and iPod Touch Backups in iTunes
http://support.apple.com/kb/ht4946
iOS: Troubleshooting Encrypted Backups
http://support.apple.com/kb/TS5162
Use iTunes to Restore your iOS Device to Factory Settings
http://support.apple.com/kb/ht1414