Add blank/empty page after every page automatically

I would use pdfpages to do this after the whole thesis is done, since you really have no need for a document with blank pages except to send to the printer, so it makes sense to keep the two documents separate.

\documentclass{article}
\usepackage{pdfpages}
\pagestyle{empty}
\begin{document}
\includepdf[pages=1-,pagecommand={\null\clearpage}]{thesis.pdf}
\end{document}

A solution with package atbegshi. It hooks into \shipout, the internal command to ship out a page. The hook (\AtBeginShipout{...} adds an empty page before the actual page except for the first.

\documentclass{article}

\usepackage{atbegshi}
\AtBeginShipoutFirst{%
  \AtBeginShipout{%
    \AtBeginShipoutOriginalShipout\null
  }%
}

\usepackage{blindtext}
\begin{document}
\blinddocument
\end{document}

Five pages are generated: 1st page, empty page, 2nd page, empty page, 3rd page.