Overlap 2 files page by page

Hello, I would want to merge 2 files, one containing the "body" of the pages and another containing some "headings, logos, etc". Say each has 30 pages.

I want to "mix" page1 with page1, then page2 with page2 and so. The final doc would be 30 pages long, not 60.

What I do now? I print doc A to a paper-based printer and then "load" that printed block of papers into the printer again and the "print document B" onto that pre-printed paper.

I would love to have that result but instead on "paper" have it on PDF.

Is this possible?