A quick solution to change PDF files page size, because Ghostscript and every single option I tested at the time just messed with the orientation. This just adjusts the MediaBox value of the file without re-encoding the images to avoid any quality loss. I intend to expand it and add executables soon.
It can only save PDFs in the 1.7 version, it doesn't seem to have a way to change this in PyMuPDF: pymupdf/PyMuPDF#3348
And they do not support PDF/A either: pymupdf/PyMuPDF#2169
I used to run MuPDF with the "mutool clean" command after running this command to ensure the PDF/A conformity would not get lost. Mutool can't convert PDFs to PDF/A, but the clean command usually helps to keep a file already formatted as PDF/A safe.