I like Paperpile’s sharing interface, but it is not good for public sharing (e.g. on Twitter). When the landing page includes a link to the PDF, the sharer (me) would likely be breaking the law due to copyright.
It would be good if, when sharing (e.g. from the PDF viewer), there was an option to share either privately or publicly; the result being the same except for the inclusion of a PDF link. This option would be best for directing traffic to Paperpile, of course.
Alternatively an option to simply “share DOI link” or “share website link” would be useful. This would also be better in that tweets etc would be included in paper’s altmetrics. This option wouldn’t direct people to Paperpile, but a “via @pprpile” could be added to tweets.