> but they're really annoying to read on a phone screen.

+1. I've already read probably 100 research papers this year in search of solutions to some technical problems, mostly while lying on bed with a tablet. I won't read as much without it.

I use an android (and iOS I think) app called Xodo. The "reader mode" re-flows the PDF into a screen-width single column like an e-book. The latest update really buried the option in the menus, but it's there somewhere and works pretty well.

How big is your phone screen and what are you using to read it? A few inches makes a lot of difference. In landscape mode my phone is 6.5" wide and reading a pdf with moonreader in full screen because its wide enough to read without having to reformat anything. You can also click on figures to view only that figure.

If that isn't enough you might consider a tablet or e-reader instead of trying so hard to make existing options work.

You CAN convert to something like epub which is trivially reflowed and this is just fine for reading fiction but just isn't as pleasant and nicely formatted as a pdf.

The software KOReader [1] has a PDF reflow setting which you can try.

[1] http://koreader.rocks/