How is it possible I created a file with 12 PDF's combined when I didn't purchase anything?

The other day, I downloaded 12 separate monthly account statements from my bank's website. Each statement was 9 or 10 pages long.

When I first downloaded the PDF for January's statement, Adobe Acrobat opened up (I guess it was the "online" version) and the Jan statement was position as a tab toward the top of the window. As I downloaded the rest of the individual statements, they proceeded to form 11 additional tabs with the titles Feb, Mar, Apr, etc. to Dec.

Somehow, after going to File/Save As and naming it the ABCwhatever account, when I subsequently reopened the file, ALL12 months were in only one tab and all 110 pages were in ONE document the pages for which were in one continuous "stream" of pages that I could scroll down through like a 110 page word document.

I've tried doing it again with other accounts and/or other years for the same account, but I can't seem to get the months to combine the way they did that first time. I know there's a "combine" command in the menu bar, but I'm not even sure if that's what "performs" the thing that I ended up with. But, even if it is, I don't have access to that command, because you have to have a subscription in order to use it......and I don't! If fact, when I click on "Combine", it brings up the window asking me if I want a 7 day free trial, so that's confirmation that I don't have it.

Anybody got any idea how I might have made that happen?