dontprint icon not appearing even on suggested test arxiv article

[blaiseli]

I tried to install dontprint on Firefox under Xubuntu 16.04. After re-starting the browser, I started following the "getting started" thing, but I can't find a dontprint icon allowing me to process pdfs, even on the example arxiv article.

The Firefox menu has a Dontprint entry, but the "Send document on this page to ..." is greyed.

How could I debug this ?

[blaiseli]

An option to convert the pdf does appear when I try to download the pdf, though.

[Stonesjtu]

Chrome on Windows 10 shares the same problem.

[CsatiZoltan]

Same with Firefox 56.0 under Windows 7. The method recommended by @blaiseli fortunately works.