We report on a measurement of the $D^{+}$-meson production cross section as a
function of transverse momentum ($p_T$) in proton-antiproton ($p\bar{p}$)
collisions at 1.96 TeV center-of-mass energy, using the full data set collected
by the Collider Detector at Fermilab in Tevatron Run II and corresponding to 10
fb$^{-1}$ of integrated luminosity. We use $D^{+} \to K^-\pi^+\pi^+$ decays
fully reconstructed in the central rapidity region $|y|<1$ with transverse
momentum down to 1.5 GeV/$c$, a range previously unexplored in $p\bar{p}$
collisions. Inelastic $p\bar{p}$-scattering events are selected online using
minimally-biasing requirements followed by an optimized offline selection. The
$K^-\pi^+\pi^+$ mass distribution is used to identify the $D^+$ signal, and the
$D^+$ transverse impact-parameter distribution is used to separate prompt
production, occurring directly in the hard scattering process, from secondary
production from $b$-hadron decays. We obtain a prompt $D^+$ signal of 2950
candidates corresponding to a total cross section $\sigma(D^+, 1.5 < p_T <
14.5~\mbox{GeV/}c, |y|<1) = 71.9 \pm 6.8 (\mbox{stat}) \pm 9.3
(\mbox{syst})~\mu$b. While the measured cross sections are consistent with
theoretical estimates in each $p_T$ bin, the shape of the observed $p_T$
spectrum is softer than the expectation from quantum chromodynamics. The
results are unique in $p\bar{p}$ collisions and can improve the shape and
uncertainties of future predictions.