Zotero provides the ability to save references from most library catalogs, databases, and regular web pages, with one click. If Zotero detects that you're looking at a book or article on a catalog, database, or a site like Google Scholar or the New York Times, you'll see a page or newspaper icon appear in the address bar of your browser. Just click the icon and Zotero will automatically save the citation. A folder icon will appear if it detects multiple items. A movie icon appears if you are saving a video. The icon on your toolbar changes according to the item type.
You can change the item types, add tags, and make notes to the saved items.
You can sort better by displaying more fields.
Check your settings - click on the gear/preferences/general/make sure automatically add PDFs is checked.
PDFs should be saved automatically, if not you can drag/drop the file into the middle Zotero pane. If PDF is restricted to Cornell users, click through to the PDF, then click on the download icon.
Storage space - 300 MB free for storage space for attachments, can save unlimited number of citations.
Unlimited space for $120/year.