We have gotten a few reports of crashes happening on the new Mac OS 10.15 (Catalina) for Papers 3. We have developed a fix and you should be able to update your Papers 3 to the new version. If you updated to Catalina before updating Papers 3 you can download the new version here:
Papers 3 Download
Upon installing, you may be asked if you'd like to "keep both" versions of Papers or "replace. Please select "replace".
After downloading you also may get an error saying that Apple "cannot check it for malicious software"
Please click "Show in Finder" and Ctrl + Click Papers and click open.
By opening Papers 3 in this manner, that alert will still pop up but you'll have the open to "open anyway" and once you click this, you will not be asked again.
If you have additional questions or issues please email us at ReadCube Papers Support