New release Adobe Acrobat PRO

I have the latest Adobe Acrobat PRO update installed and there are problems when I add a file to an existing document. The newly added document appears with different dimensions and proportions to the existing document, which was not the case with the old version. Furthermore, I find the operation of editing documents very cumbersome and above all it is not possible to add a background (e.g. a letterhead file) to an existing document, because the file added is always of proportions and dimensions that are not compatible with the existing one. Is there by any chance an update planned that can correct these obvious flaws, or is there any option that can be added or that can change and eliminate the problems?
Thank you for your answers and advice!