Combine parts of pages of a PDF document

I have a PDF which has some content split onto 2 pages.

The first part takes less or equal the bottom half of the first page and the second part takes less than the top half of the second page. For example, if x is the wanted content on the first page and y is the wanted content on the second page and - is the content I don't want to be in the output document we have:

|-|  |y|
|-|  |y|
|-|  |-|
|x|  |-|
|x|  |-|

And I'd like to have

|x|
|x|
|y|
|y|

on one page.

Is it possible to merge these parts that way on Linux?