Hello all together
I have the same issue here. 20-paged brochure, quite graphic heavy (a background image on every page, pictures). I also have some PDF files with vectorized text. I had to convert the text into vectors because Publisher does not just place a PDF with included fonts into the document but rather "opens" the file; so all of the fonts are completely messed up.
The export takes about 3 hours. However, the exported PDF file isn't that big (62 MB, which is the normal size for a high-end print PDF). I tried different settings, but even the low-res export takes about 2 hours.
These are my settings: MacBook Pro (Retina, 15-inch, Mid 2015) 2.2 GHz, macOS 10.14.6, 16 GB RAM, Publisher v.1.7.3