No, /MediaBox is inheritable.
I am not talking about PDF. What about PDF/X?
I don't know (I don't have the standard) and I can't test.
Can somebody confirm this?
Version 3 says nothing about inheritance (see quoted below). I'll try to get the newest PDF/X spec. However, some apps may treat inherited boxes different; afaik Acrobat don't display boxes if inherited from /Pages -) #### PDF/X-3:2002 "_2.9 Box usage and management_ The inclusion of the bounding boxes as specified in Portable Document Format Reference Manual, Version 1.3, Second Edition, is a required operation in the process of creating a PDF/X file. For all PDF files, the MediaBox is required. Additionally, each PDF/X page shall include either an ArtBox or TrimBox, but not both. The inclusion of a BleedBox is optional. If a BleedBox is present, neither the ArtBox nor the TrimBox may extend beyond the boundaries of the BleedBox. In the case where the CropBox is present, neither the ArtBox nor the TrimBox may extend beyond the boundaries of the CropBox. The bounding boxes may be used by PDF/X-compliant pagination applications to automatically position the file in a predetermined space within a layout construct. Within some industry workflows, both the BleedBox and TrimBox are necessary. For example, commercial, non-newspaper printing may include large numbers of pages containing bleed and trim information. It is important that boxes that represent this information be included. The accurate inclusion of the BleedBox and TrimBox will allow for the correct portion of the file to be imposed and rendered, and appropriate automation to be applied. NOTE: The use of TrimBox is recommended in preference to ArtBox." -- Pawe/l Jackowski P.Jackowski@gust.org.pl