On Wikimedia Commons (i.e. the version running there), the file
File:Finlands Allmänna Tidning 1820-01-03.pdf
doesn't show any page images.
Adding ?action=purge to the URL doesn't help.
No explanation is given.
In an offline reader, the PDF looks fine.
If the images are encoded in a way that MediaWiki can't handle,
the user would be helped by an error message that gives
instructions on which image encodings are supported.