Hello,
I'm using Dropbox API v2.
Currently, PDF file thumbnail is not supported on document.
https://www.dropbox.com/developers/documentation/http/documentation#files-get_thumbnail
This method currently supports files with the following file extensions: jpg, jpeg, png, tiff, tif, gif and bmp. Photos that are larger than 20MB in size won't be converted to a thumbnail.
However, I look that get_thumbnail api can get the pdf thumbnail now.
Will you update specification?