Replace natbib by biblatex to get citation links

\usepackage[backend=bibtex, style=authoryear-comp, natbib=true, sortcites=false]{biblatex}
\addbibresource{main.bib}

% optional if you want (Smith 1776) instead of (Smith, 1776)
\renewcommand*{\nameyeardelim}{\addspace}

\begin{document}
% . . .
\printbibliography
\end{document}