Upload results in EMPTY PDF !

hello world,
I installed edocman 1.8.9 in joomla 3.8.1 and uploaded some pdfs. They apear in the category listing as they should... but when I want to view them I get a white, empty page. Even the details show filesize : EMPTY. So i guess, I have an upload problem, to be more detailed a permission problem. But I have no idea, what folder I have to give which permission ?

I suppose edocman to have a pdf-viewer integrated, or do I have to install a pdf viewer additionally ?

Any help is welcome !

I have having the same problem after upgrading.

Hi Chris,
With this kind of issue, you need to submit ticket and send your site url with super admin account. I'll check the problem for you
Thanks
Dam