I am afraid that there's no automated way to split the pages using PDF tools.
If your A0 files contain more than one page, then it might be possible to e.g. use the "crop" tool inside PDF Tools, and to crop the same area of multiple pages in one go. After that you can repeat the crop process for the second area of the A0 files, etc. That way if you e.g. merge all files into one - you will need to do the crop operation only 16 times. And then rearrange the cropped files as needed.