How to Add/Change Reflow property for PDF files

Reflow option need to be enabled if you want to read PDF files on small screens (smartphones, PDA-s, eBook readers etc). In most cases downloaded PDFs don't have setted this option, and you can't easy set that.
I found only one method:

First you need program FineReader. In that program than open your PDF file. Than you need to call Read all pages (this is procedure where FineReader goes through all pages and prepare texts and paragraphs):

When "reading" is finished, you can save your PDF. In save dialog pick pdf:

and in format setings check "enable tagged PDF".

And that's all. Wait some time and your new reflowed document is ready.