You can easily combine two or more Paperless 2 receipt and/or document libraries into a single 3.0 library.

- Launch Paperless 3
- Select File > Open and choose your Paperless 2 library.  Upgrade the Library when prompted
- Repeat that step for each of your Paperless 2 libraries
- Open the upgraded library you'd like to use as your main Paperless 3 library
- Select File > Import Library and choose an upgraded library to combine with your existing library
- Repeat that step for each of the upgraded libraries you'd like to merge with your main library file