How to invert pdf even and odd pages?

Question

I have good amount of PDFs, and I noticed that some of them, have pages in a wrong order:

Right Order: 1-2-3-4-5-6-7-8-9-10...120-121

Wrong order: 1-2-4-3-6-5-8-7-10-9...121-120

The first 2 pages are ok, but the other ones, are totally messed up.

As you can see, I'd have to invert, one by one, the order of the pages, if I had to do that manually.

Searching online, I found that 2 nice tools are qpdf and pdftk, which could help me solving this problem, but I really don't have any exeperience using them.

Could you guys help me out with a qpdf/pdftk command/bash script? (Or with an alternative of coourse, why not. Just keep in mind, that programs with a graphical interface, may not be suitable for this job, as this problem is present in more than 100 files and doing it manually isn't a bright option).

Answer 1

Using qpdf page-selection documentation:

qpdf wrong.pdf --collate --pages . 1,1,3-z:even . 2,2,3-z:odd -- right.pdf