Add possibility to paginate only single pdf pages.

[DunklesArchipel]

In general, and especially for long pdf files, it is sometimes desirable to paginate only pages including the data of interest.

I am not sure how exactly this click interface works but I assume it could be something like this:

• --pages 3
• --pages 3-5
• --pages 3,6-7

[saraedum]

We could probably use something like this: https://stackoverflow.com/a/4248689