The other day I needed to prepare one PDF file for the site. Yes, that's bad luck, it was necessary to collect it from 3 PDF files, and one of them also removed the page in the middle.
Search solutions on the Internet. There were solutions, but under Windows (and not free), then in Java with a bunch of dependencies, then strange console strings of commands ...
And now, the winning character set is entered in the search box of the Ubuntu application center:
')

Double click on the found record and read ...
PDF Shuffler
It is a small application that allows you to use it.
License: Open Source
Cost: Free
Great, I decided and pressed the "Install" button.
The program with dependencies - several tens of kilobytes was installed quickly and was used immediately for its intended purpose. The program interface is masterpiece:

Drag and drop files from Nautilus with the mouse, select the unnecessary pages from them, click “Export PDF”.
Everything. I was happy.
I hope this program will help you!