When you sync your library to download articles from our cloud server, you only initially download the article's metadata. The PDF files themselves remain on the cloud until you highlight the article in your library and select the "download" button. We arranged the process like this to not fill up the hard drive space of smaller devices as well as expedite the sync process, which otherwise would take much longer. To download multiple articles/a full list, you will need to manually download each article one at a time (their metadata will sync with just the press of the sync button).  We are working on a more elegant solution for this in the future.