Before you install, Greasy Fork would like you to know that this script contains antifeatures, which are things there for the script author's benefit, rather than yours.
This script is only fully functional after you sign up for something, like joining a group, subscribing to a channel, or liking a page.
The author of this script explains:
百度文库需要输入验证码之后才能下载，豆丁网和道客巴巴可直接导出