  Superconducting gap structure was probed in type-II Dirac semimetal PdTe$_2$
by measuring the London penetration depth using tunnel diode resonator
technique. At low temperatures, the data for two samples are well described by
weak coupling exponential fit yielding $\lambda(T=0)=230$~nm as the only fit
parameter at a fixed $\Delta(0)/T_c\approx 1.76$, and the calculated superfluid
density is consistent with a fully gapped superconducting state characterized
by a single gap scale. Electrical resistivity measurements for in-plane and
inter-plane current directions find very low and nearly temperature-independent
normal- state anisotropy. The temperature dependence of resistivity is typical
for conventional phonon scattering in metals. We compare these experimental
results with expectations from a detailed theoretical symmetry analysis and
reduce the number of possible superconducting pairing states in PdTe$_2$ to
only three nodeless candidates: a regular, topologically trivial, $s$-wave
pairing, and two distinct odd-parity triplet states that both can be
topologically non-trivial depending on the microscopic interactions driving the
superconducting instability.
