Mekentosj Papers and Dropbox: get a bit more space

I use Dropbox to keep an automatic backup of my Papers library. However, I was scraping close to my space allowance, and discovered that Papers adds some temporary files to the "Library.papers2" folder that eat up precious cloud space. Here is how to remove them from Dropbox:

1. Quit Papers 2.0. Make a backup of your Papers library.
2. Go to the "Library.papers2" folder inside your Papers library.
3. Copy the folders "Thumbnails" and "Spotlight" somewhere (e.g. your Desktop). The other folders don't need much space in my case.
4. Click the Dropbox icon in the menu bar, navigate to Preferences, Advanced, Selective Sync and de-select the "Thumbnails" and "Spotlight" folders. (Dropbox will now delete the folders.)
5. Move the folders you copied before back into the "Library.papers2" folder.
6. Via Dropbox's web interface, delete the online version of the two folders.
7. Voila: more space (200 MB, in my case).