This may be a way to promote their other Android app, Foxit PDFCreator which costs about $5.
Looking at the Play Store comments will show you that Foxit Mobile PDF received much criticism for not being updated for a long time.
A small list of the app’s features:
View PDF documents
Annotate and comment on PDF documents
Outline / Bookmark / Annotation management
Public cloud integration
Portrait / Landscape screen mode
You can view a more detailed list of features at the Play Store page linked in the widget at the bottom of the post.
While there isn’t an official announcement of the price drop, we found a link in Google’s search results which shows it’s older price was $2.99.
Thanks to our friend Arnab for the tip.
We will update this post if we find a change-log or an official announcement from Foxit.