(Website is gone, repo is stale: https://github.com/robamler/dontprint. It uses k2pdfopt.)
But it's being kept up to date and it's an active project!
It's great for following your favorite scientists and professionals, and now I favorite more of their posts, which makes me happy because I feel like I am spreading more love in the world.
edit: fyi it's originally because the information about Encryption Compliance is so confusing. I just use HTTPS and I'm pretty sure the documentation has gotten clearer in the meantime, so I'm optimistic.
And please consider that some who'd like to use k2pdfopt on the iphone don't use Twitter at all, I have a sure example of one, and I hope I could use your app independently from that?
If you copy-paste, or copy and use the clipboard button, it will try to identify the arXiv identifier from the url, and then show you the title + abstract. Then you have to download the PDF, preview the transformed copy (copy stays in the cloud for 24h), and finally request a fully reflowed copy. The reflow is limited to about 30s via AWS Lambda, so this is not for dissertations -- this is for 2-20 page papers you can reasonably read on your phone. Nevertheless, there is a progress bar at the top of the screen to show you it's working, at that stage. These steps are pretty much reproduced in the app store images.
For a non-arXiv link, the only difference is that there is no abstract. But note, the link can't just be to the journal page, you've got to get a PDF mime-type when it's requested.
There are some things I should change, but it's very useful to me, and I just verified it works for both arXiv and non-arXiv. If it's not working for you, I would suggest deleting and reinstalling (sorry!).
That was only on August 3 2019 :-)
Just because you're not using the grooviest library or haven't been writing C++17 doesn't mean your application, which still functions on its target plaforms, is obsolete.
Calibre can convert between the ebook formats.
k2pdfopt -om 0.15 -w 800 -h 1732 <file-name>
k2pdfopt $* -dev kpw -mode fw -wrap -hy -ws 0.375 -ls-