I was wondering why we should pay for cloud space to store our PDFs. Can they not just be files synced with google drive or some other could service that people already use? Is there a web viewer?
Yes there is a web viewer (see "Web Library" at the top of this page). There's also an iOS app under development. While there are options to use other services for file sync for personal libraries (see https://www.zotero.org/support/sync#file_syncing ), none of them work for files in groups (which require more complex permission handling then can reasonably be done through a 3rd party service) and none of them work as seamlessly for both set-up and day-to-day usage as Zotero storage. FWIW, file storage is also Zotero's only source of revenue, so it directly supports Zotero's ongoing development.
All that said, there's absolutely no obligation to pay Zotero for file storage, and the software is fully functional (except file-sharing in groups) without it.
Upgrade Storage
While there are options to use other services for file sync for personal libraries (see https://www.zotero.org/support/sync#file_syncing ), none of them work for files in groups (which require more complex permission handling then can reasonably be done through a 3rd party service) and none of them work as seamlessly for both set-up and day-to-day usage as Zotero storage.
FWIW, file storage is also Zotero's only source of revenue, so it directly supports Zotero's ongoing development.
All that said, there's absolutely no obligation to pay Zotero for file storage, and the software is fully functional (except file-sharing in groups) without it.