Sorry to inform you that you cannot Add or Delete pages in Adobe PDF Pack. FAQ | Adobe PDF Pack
For that, you need Adobe Acrobat DC. Answers to some of the most frequently asked questions about Acrobat DC
If you wish you can use the trial version. You can download the Adobe Acrobat DC trial version from here: Download Adobe Acrobat free trial | Acrobat Pro DC
Let us know if you have any question or need any help.