When you've run out of storage you won't be able to add new PDFs to your Locker.
You can free up space by removing PDFs. To do so, head to https://kopernio.com/locker. If there are any PDFs you no longer need, you can remove them by clicking the [x] button on the bottom right corner of the PDF tile.
Alternatively, you can opt to spread the word and increase your Locker storage. When a new user joins Kopernio through your personal referral link we automatically upgrade your account to Kopernio Premium. This means 2 GB of storage and unlimited tagging.
Just follow this link to get started https://kopernio.com/premium.