Best format for self-publishing?

I have a little short story almost ready, but I'm unsure about how exactly I should present it.

A4 is best for normal printing. But the lines are too long for comfort unless you make the margins really big.

A5 looks good on screen and zine printing is pretty easy with Acrobat Reader. But A5 sucks for normal A4 printing.

I could also create a ready-to-print booklet with two A5 pages on each A4. But that can only be printed, not read on the screen.

I could also just put the story online, to be read without the potential reader having to actively download it. But I feel that there is something a bit shallow about the web medium. We're skimming stuff more than we read. So I would prefer a download.

 

In theory, yes. But if we look at this forum, we need to make double line breaks for paragraph breaks, and the lines continues far too long for comfort. Might look better on a mobile phone. Still, I think an A5 .pdf is a safer bet. For some reason, the .pdf has become a standard for "serious digital publishing". Perhaps because it's less cluttered than your average web page.

The .epub format can work pretty well for electronic reading, but not everyone use it.