This is a bit of a negative answer but I thought it relevant to the topic. As of August 2013 it doesn't appear that the upstream tool to Evince, as well as other PDF viewers on Linux, supports this feature. This upstream tool is called Poppler and according to this question on one of the development forums for Poppler, titled: [poppler] Reflow Feature Support in Poppler it isn't supported.
The other thing that caught my eye from this thread was this bit about Acrobat's support of this feature:
excerpt
Does poppler support reflow feature?
No.
>
I have poppler -0.12.1 version .
Can i get any help or documentation for reflow implemantation?
If this is for display on small devices, remember there are other
approaches. Acrobat's reflow feature relies upon tagged pdfs (which
are not all that common), or guessing the layout, much as poppler does
for text extraction. One alternative is therefore to use poppler's
text extraction and /not/ display the document as a pdf; eg use
pdf2txt or pdf2html and rely on a browser to do reflow. That's what
this bug is about: https://bugs.freedesktop.org/show_bug.cgi?id=20652
That same thread goes on to highlight a couple of other alternatives to reflow that might be worth looking into.
Alternatives
These tools do not offer live reflow functionality, rather they reformat the PDF using a variety of other techniques. Most of them take a file in, reformat it, and spit out a modified version of the original.
Pdfreflow
Pdfreflow is a command line tool that reflows PDF text. Its input is the XML output of pdftohtml, to which it reflows the text, removes page number, header, footers, and hyphenation, and generates an HTML file output.
Briss Lifehacker review
Briss, a cross-platform open-source tool, gives you several ways to trim PDFs to look better on your ereader.
K2pdfopt Howtogeek review
K2pdfopt is designed to optimize PDF documents for small screen e-readers. Rather than convert the document into raw text and try to reformat it, it instead carefully crops and realigns the pieces as though they were a series of images. The end result is a new PDF file that is really true to the original document and free from odd OCR blunders (as it doesn’t attempt to convert or reflow the text).
Calibre
ebook management software.