If you need to work offline for a longer period of time, you can save all attachments from your cloud project locally:
1.In yor Citavi project, on the File menu, click This project.
3.Switch to the Attachments tab.
4.Click Save all attachments locally (for working offline).
A pop-up window will appear in the bottom right to let you know that the download has started. Repeat these steps each time you want to work offline.
Citavi saves downloaded PDFs in the folder C:\Users\YOUR NAME\AppData\Local\Swiss Academic Software\Citavi 6\ProjectCache. Citavi can only use the files as long as you do not make any changes to the folder (renaming files, moving files, etc.).