I am using MS Publisher 2016 from an active Office 365 subscription.
I have read this post and I believe that changing the source page size is WRONG. I have one page in Publisher set to poster A3, which I want to print to ALL the following: a big A3 poster, a regular A4 page as well as a small A5 leaflet. I do not want to manually resize all and scale fonts, etc. This is simply crazy.
The solution I have found is to design the page at the largest size, e.g., A3, export to PDF according to the page size. Then I import it into GIMP at 300 dpi, then go to image / scale and select "lock aspect ratio" and "cm" and then set the exact PAPER size I want for each one, I resize then I export to PDF or JPEG under a new file name.
GIMP imports all fonts and graphics and converts them to a single one page-sized bitmap, then scales it to either the medium A4 page or the smaller A5 leaflet.
Anyway I still find this totally CRAZY. Publisher shall have the option of SCALING THE SOURCE PAGE TO FIT THE TARGET PAPER as alternative to tiling.