```
\documentclass{standalone}

\usepackage{pgfplots}
\usepackage{pgfplotstable}
\pgfplotsset{compat=1.10}

\pgfplotstableread{
0.01    1.00
0.02    2.00
0.03    3.00
0.04    4.00
0.05    5.00
}\datatable

\begin{document}
\begin{tikzpicture}
\begin{axis}[ymin=0, ymax=6]
\addplot table  {\datatable}
node[pos=0.0, pin=above:"Unidentified peak"]{} % pos only allows for fractional value
node[pos=0.2, pin=above:"Bragg peak"]{} % pos only allows for fractional value
node[pos=1.0, pin=above:"my custom label"]{} % pos only allows for fractional value
;

\end{axis}
\end{tikzpicture}
\end{document}

```

**UPDATE:**
A slightly shorter version of the second solution in the answer by @Matthew Leingang:

```
\documentclass{standalone}

\usepackage{pgfplots}
\usepackage{pgfplotstable} % For \pgfplotstableread
\pgfplotsset{compat=1.10}

\pgfplotstableread{
0.01    1.00
0.011   2.00
0.012   3.00
0.013    4.00
0.05    5.00
}\datatable
% \pgfplotstableread{results.dat}\datatable

\pgfplotstablegetrowsof{\datatable}
\pgfmathsetmacro{\N}{\pgfplotsretval}  

\begin{document}
\begin{tikzpicture}
\begin{axis}[ymin=0, ymax=6]
  \addplot+[mark=none, forget plot] table {\datatable};
  \addplot+[only marks] table  {\datatable}
    % pos = (index-1)/(N-1)  (index starting from 1)
    node[pos=(1-1)/(\N-1), pin=right:first point (1/\N)]{}
    node[pos=(3-1)/(\N-1), pin=-45:third point (3/\N)]{}
    node[pos=(4-1)/(\N-1), pin=-45:end of linear behaviour (4/\N)]{}
;
\end{axis}
\end{tikzpicture}
\end{document}

```

![enter image description here](https://i.stack.imgur.com/lFsED.png)