Latest APub on Win 10 x64
To reproduce:
The use case was a big banner to be viewed from a large distance. So make a project in a decent size, maybe 2m x 1m
Drag some (medium-res) images in and make them fit the big page.
Their actual resolution will be quite low (e.g. 40dpi)
Export the project to PDF using a dpi that's higher than that of the images (e.g. 60dpi).
Check the resolution of the images in the resulting PDF:
What should have happened is, that things like transparencies are flattened using 60dpi resolution, and the images remain at their lower native resolution.
But instead, the images will have been upscaled to the document resolution (here 60dpi)
That doesn't make sense to me, the upscaling is not really introducing better quality. It only increases the file size.
Some people reported this only happens with PDF/X files, I did not have time to check this.
See also the original question posed in the forum: