@kicr
Thats the reason why your downloads are failed: Because with Joomla-enabled-gizp your content get zipped twice because your server itself does gzip.
So your problem is solved when you disable gzip in joomla.
@stefanato
Thanks for your test page, please switch to the other topic (
www.joomlaeventmanager.net/forum/jem-2-2-x-on-joomla-3/10486-corrupted-pdf-download-from-attachements
) because this topic is about not downloading pdfs. Your pdfs are corrupted. It keeps the forum clear.