test.pdf wasn't a valid PDF file:
>$ mutool info test.pdf
>test.pdf:
>error: cannot recognize xref format
>error: cannot read xref (ofs=406)
>error: cannot read xref at offset 406
>warning: trying to repair broken xref
Process it with `mutool clean` to fix errors, collapse newlines to reduce size
ClosesHomebrew/homebrew#38194.
Signed-off-by: Xu Cheng <xucheng@me.com>