To back up your library, head to the ReadCube desktop app and navigate down to preferences and support. From there, you'll see some options for "Library Export":
Here you can export just your library which will maintain your library structure, highlights, and notes or export your library as well as the actual PDFs by selecting "export files". If you are planning on migrating your ReadCube library to another computer or wish to back up everything be sure to check off "export files" otherwise only the metadata will come over and not your actual PDFs.
Once it's exported, keep it somewhere safe such as an external hard drive in case of an emergency.
Details about the format options:
To migrate your library - for example, to a new computer - choose the ReadCube Archive option. Select the "Export Files" checkbox to include PDFs. This option will create copies of the files in a new folder at the export location and may take a significant amount of time depending on your library size. If unchecked, only reference metadata will be exported.
To import your library on a different computer, simply use the regular Import screen to drag in just the .rc file. If the "Export Files" option was selected, we'll attach the PDFs automatically; just make sure the .data folder containing the PDFs is in the same location as the .rc file. All imported PDFs will be copied to the default folder location ("ReadCube Media" in your Documents folder). This setting can be changed in Preferences-General.
For inter-compatibility with other software, please choose the .bib export option.If you run into any issues, please feel free to contact us at firstname.lastname@example.org.