Koofr is a storage service that offers up to 10GB of free safe storage (initially you get 2GB and you can get up to 8GB by inviting friends to join Koofr) for your files with affordable upgrades and options to connect multiple cloud accounts. You can sign up to this storage service via my invite link http://k00.fr/npeutcoc.
You can find detail instruction on how to sync Zotero library to your Koofr’s account via WebDAV here. Basically, the steps I performed in Arch Linux are as follows. One can also find a list of WebDAV services which provide a free plan and which users have reported success using with Zotero here.
Edit -> Preferences.
Settingssection, type in your Zotero Username and Password required in the
Data Syncingsubsection and click
Set up Syncing.
File Syncingsubsection, tick to the box
Sync attachment files in My Library using, and then choose
WebDAVin the dropdown menu. Next, type
app.koofr.net/dav/Koofrinto the URL text box, and type your Koofr’s email and password respectively into the Username and Password text boxes.
Verify Server. A window will pop-up to let you know that file sync is successfully set up and a folder named
zoterowill be created in Koofr when that happens. Every title you add to your Zotero Library and has an attachment will be synchronised to Koofr and you will find it in
zoterofolder in Koofr as a
I use the app PaperShip to sync my Zotero library to my iPhone and iPad. The Koofr’s WebDAV server address is
https://app.koofr.net/dav/Koofr. Note that one needs to create a
lastsync.txt file (which may be empty) in the
zotero folder in Koofr as instructed here in order to make PaperShip correctly verifies the WebDAV server.