A5 paper size wrong
The paper size for A5 in the presets is technically wrong as it should be 148.5mm wide and not 148mm. You can't change the built-in presets but it would be really helpful to do so as our onward print workflow relies on 148.5mm wide files and it's really annoying to have to change it after it's all been designed if you forget to change the page size at the beginning.
A5 is exactly 148×210 mm and the customer has confirmed that there is nothing to fix.
Adobe InDesign Team
Peter Villevoye commented
For the ISO standard, the DIN institute has rounded off the exact sizes of the A-series to whole mm values. So going from A4 to A5, the rounding-off flips, and cuts the smaller half of the mm. (Hence the 297 mm for A4 is actually a bit too large...)https://en.wikipedia.org/wiki/ISO_216
Steve Edwards commented
A5 technically is 148.5mm x 210mm (half of 297mm is 148.5mm). Our systems anyway require documents to be setup at 148.5mm. It would just be useful to be able to change the built in sizes.
A5 is exactly 148x210 mm, there is nothing to fix...