Changing attachment size limit

Trying to drag and drop or paste pdf files greater than the 10 MiB limit pops up an error. Searching around I find that there is an undocumented setting to set this limit: maximumDocumentSize (from here: Document is too large, maximum is 10MiB).

So, I create a CONFIG page in my space and add a space-lua block with:

config.set("maximumDocumentSize", 100000000)

which I hope will up the limit to 100 MiB.
I still receive the error when pasting a pdf file that is ~14MiB in size.

Does this setting still work? Is there something obvious I'm doing wrong?

Thanks for any help!